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Здесь приведён неполный список работ, опубликованных сотрудниками кафедры в последнее время.

Эти работы дают представление о научных направлениях, представленных на кафедре, интенсивности и качестве научной работы.


 

New mechanism of the formation of vacancy voids

Devyatko, YN; Khomyakov, OV; Kagan, MY

LOW TEMPERATURE PHYSICS; vol. 36;issue 4; pp. 313-316; year: 2010

Abstract: A new mechanism is proposed for the formation of vacancy voids in irradiated metal as being due to the successive development of two types of instabilities in a system of interacting point defects produced by neutron irradiation. The first stage of the void formation process involves the nucleation of local vacancy clusters possessing a high, relative to the surroundings, concentration of defects; the second state involves lattice instability inside such clusters. (C) 2010 American Institute of Physics. ___________________________

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Multiple Colliding Electromagnetic Pulses: A Way to Lower the Threshold of e(+)e(-) Pair Production from Vacuum

Bulanov, SS; Mur, VD; Narozhny, NB; Nees, J; Popov, VS

PHYSICAL REVIEW LETTERS; vol. 104; issue 22; year: 2010

Abstract: The scheme of a simultaneous multiple pulse focusing on one spot naturally arises from the structural features of projected new laser systems, such as the Extreme Light Infrastructure (ELI) and High Power laser Energy Research (HiPER). It is shown that the multiple pulse configuration is beneficial for observing e(+)e(-) pair production from a vacuum under the action of sufficiently strong electromagnetic fields. The field of focused pulses is described using a realistic three-dimensional model based on an exact solution of the Maxwell equations. The e(+)e(-) pair production threshold in terms of electromagnetic field energy can be substantially lowered if, instead of one or even two colliding pulses, multiple pulses are focused on one spot. The multiple pulse interaction geometry gives rise to subwavelength field features in the focal region. These features result in the production of extremely short e(+)e(-) bunches.

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High-order harmonic generation in clusters irradiated by an infrared laser field of moderate intensity

Zaretsky, DF; Korneev, P; Becker, W

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS; vol. 43; issue 10; year: 2010

Abstract: Extending the Lewenstein model of high-order harmonic generation (HHG) in a laser-irradiated atom, a model of HHG in a cluster is formulated. The constituent atoms of the cluster are assumed to be partly ionized. An electron freed through tunnelling may recombine either with its parent ion or with another ion in the vicinity. Harmonics due to the former process are coherent within the same cluster and may be coherent between different clusters, while harmonics due to the latter process are incoherent. Depending on the density of available ions, the incoherent mechanism may dominate the total harmonic yield, and the harmonic spectrum, which extends to higher energies, has a less distinct cutoff and an enhanced low-energy part.

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Neutral weak currents in nucleon superfluid Fermi liquids: Larkin-Migdal and Leggett approaches

Kolomeitsev, EE; Voskresensky, DN

PHYSICAL REVIEW C; vol. 81; issue 6; year: 2010

Abstract: Neutrino emission in the processes of breaking and formation of nucleon Cooper pairs is calculated in the framework of the Larkin-Migdal and Leggett approaches to the description of superfluid Fermi liquids at finite temperatures. We explain peculiarities of both approaches and explicitly demonstrate that they lead to the same expression for the emissivity in pair breaking and formation processes.

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Amplification of a high-frequency wave by IR-field-heated clusters

Korneev, P; Becker, W

LASER PHYSICS LETTERS; vol. 7; issue 6; pp. 440-449; year: 2010

Abstract: The nonequilibrium nanoplasma created by irradiation of a cluster, or other nanosystems such as large molecules, with an intense infrared-laser field may be used as an amplifying medium for a high-frequency probe field. We employ a simple description where the nanosystem is modeled by particles bound by a self-consitent potential. An incident probe field suffers gain or loss depending on the respective parameters by a mechanism that is usually referred to as collisionless damping. The model is simple enough to allow for an essentially analytical solution.

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High-order harmonic generation by an intense infrared laser pulse in the presence of a weak UV pulse

Popruzhenko, SV; Zaretsky, DF; Becker, W

PHYSICAL REVIEW A; vol. 81; issue 6; year: 2010

Abstract: High-order harmonic emission by an atom subject to the superposition of a strong infrared (IR) and a weak ultraviolet (UV) laser pulse is studied for the case when the UV photon energy remains below the ionization threshold. A simple analytical treatment is developed on the basis of the Lewenstein approach modified to account for the contribution of excited bound states of the atom. It is found that an order-of-magnitude enhancement of the high-harmonic emission rate can be expected, particularly in IR fields of moderate intensity. The results are discussed in view of recent experimental data and numerical simulations of the problem.

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Unconventional Application of the Two-Flux Approximation for the Calculation of the Ambartsumyan-Chandrasekhar Function and the Angular Spectrum of the Backward-Scattered Radiation for a Semi-Infinite Isotropically Scattering Medium

Remizovich, VS

LASER PHYSICS; vol. 20; issue 6; pp. 1368-1389; year: 2010

Abstract: It is commonly accepted that the Schwarzschild-Schuster two-flux approximation (1905, 1914) can be employed only for the calculation of the energy characteristics of the radiation field (energy density and energy flux density) and cannot be used to characterize the angular distribution of radiation field. However, such an inference is not valid. In several cases, one can calculate the radiation intensity inside matter and the reflected radiation with the aid of this simplest approximation in the transport theory. In this work, we use the results of the simplest one-parameter variant of the two-flux approximation to calculate the angular distribution (reflection function) of the radiation reflected by a semi-infinite isotropically scattering dissipative medium when a relatively broad beam is incident on the medium at an arbitrary angle relative to the surface. We do not employ the invariance principle and demonstrate that the reflection function exhibits the multiplicative property. It can be represented as a product of three functions: the reflection function corresponding to the single scattering and two identical h functions, which have the same physical meaning as the Ambartsumyan-Chandrasekhar function (H) has. This circumstance allows a relatively easy derivation of simple analytical expressions for the H function, total reflectance, and reflection function. We can easily determine the relative contribution of the true single scattering in the photon backscattering at an arbitrary probability of photon survival.. We compare all of the parameters of the backscattered radiation with the data resulting from the calculations using the exact theory of Ambartsumyan, Chandrasekhar, et al., which was developed decades after the two-flux approximation. Thus, we avoid the application of fine mathematical methods (the Wiener-Hopf method, the Case method of singular functions, etc.)and obtain simple analytical expressions for the parameters of the scattered radiation. Note that the simplicity of the expressions is supplemented with unexpectedly high accuracy. The results demonstrate the unknown possibilities offered by the two-flux approximation, which is the simplest approximate method to solve the equations of transport theory. We assume that the method can be employed in the calculations of the angular characteristics of the reflected radiation for media whose single scattering is described using complicated (in comparison with isotropic) laws.

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Viscosity coefficients for hadron and quark-gluon phases

Khvorostukhin, AS; Toneev, VD; Voskresensky, DN

NUCLEAR PHYSICS A; vol. 845; pp. 106; EP 146; year: 2010;

Abstract: The shear (eta) and bulk (zeta) viscosities are calculated in a quasiparticle relaxation time approximation. The hadron phase is described within the relativistic mean-field-based model with scaled hadron masses and couplings. The quark phase is treated in terms of the heavy quark bag model fitted to the lattice data. A two-phase model allowing for the first-order phase transition from the hadron phase to the strongly coupled quark-gluon plasma is constructed by means of the Gibbs conditions. Temperature and baryon density dependence of the calculated viscosity-to-entropy ratios (eta/s, zeta/s) are analyzed and compared with those obtained in other models. Special attention is paid to the behavior of viscosity coefficients near the critical temperature, from both hadron and quark gluon side. Effects of resonance widths on viscosities and viscosity-to-entropy ratios are estimated. (C) 2010 Elsevier B.V. All rights reserved.

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Limitations on the Attainable Intensity of High Power Lasers

Fedotov, AM; Narozhny, NB; Mourou, G; Korn, G

PHYSICAL REVIEW LETTERS; vol. 105; issue 8; year: 2010

Abstract: It is shown that even a single e(-)e(+) pair created by a superstrong laser field in vacuum would cause development of an avalanchelike QED cascade which rapidly depletes the incoming laser pulse. This confirms Bohr's old conjecture that the electric field of the critical QED strength E-S m(2)c(3)/eh could never be created.

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Particle-hole optical model and strength functions for high-energy giant resonances

Urin, MH

PHYSICS OF ATOMIC NUCLEI; vol. 73; issue 8; pp. 1384-1389; year: 2010

Abstract: A formulation of the particle-hole optical model is proposed for describing the contribution of the fragmentation effect to the formation of strength functions for high-energy giant resonances. The model is based on the Bethe-Goldstone equation for the energy-averaged particle-hole Green's function. In this equation, the particle-hole interaction that is induced by a virtual excitation of multiquasiparticle configurations and in which, upon averaging over energy, an imaginary part is contained is taken into account. An analogy with the single-quasiparticle optical model is discussed.

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Thermal conductivity in dynamics of first-order phase transitions

Skokov, VV; Voskresensky, DN

NUCLEAR PHYSICS A; vol. 847; issue 3-4; pp. 253-267; year: 2010

Abstract: Effects of thermal conductivity on the dynamics of first-order phase transitions are studied. Important consequences of a difference of the isothermal and adiabatic spinodal regions are discussed. We demonstrate that in hydrodynamical calculations at non-zero thermal conductivity, kappa not equal 0, onset of the spinodal instability occurs, when the system trajectory crosses the isothermal spinodal line. Only for kappa = 0 it occurs at a cross of the adiabatic spinodal line. Therefore ideal hydrodynamics is not suited for an appropriate description of first order phase transitions. (C) 2010 Elsevier B.V. All rights reserved.

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Vector statistics of multiply scattered light in a random medium with large inhomogeneities

Gorodnichev, EE; Kuzovlev, AI; Rogozkin, DB

LASER PHYSICS; vol. 20; issue 11; pp. 1961-1967; year: 2010

Abstract: The distribution function of the scattered radiation intensity is calculated in the approximation of the basic polarization modes. In such an approximation, the distribution function is represented in terms of the degree of polarization of the initially circularly and linearly polarized waves transmitted by the sample. The effect of the difference of the decay rates for the circular and linear polarization modes on the statistics of the light waves that are multiply scattered in the medium with large inhomogeneities is analyzed.

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Quantum dot version of topological phase: Half-integer orbital angular momenta

Mur, VD; Narozhny, NB; Petrosyan, AN; Lozovik, YE

JETP LETTERS; vol. 88; issue 10; pp. 688-692; year: 2009

Abstract: We show that there exists a topological phase equal to pi for circular quantum dots with an odd number of electrons. The non-zero value of the topological phase is explained by axial symmetry and two-dimensionality of the system. Its particular value (pi) is fixed by the Pauli exclusion principle and leads to half-integer values for the eigenvalues of the orbital angular momentum. Our conclusions agree with the experimental results of T. Schmidt et al., Phys. Rev. B 51, 5570 (1995), which can be considered as the first experimental evidence for the existence of the new topological phase and half-integer quantization of the orbital angular momentum in a system of an odd number of electrons in circular quantum dots.

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Effects of nondiffusive wave propagation upon coherent backscattering by turbid media

Marinyuk, VV; Rogozkin, DB

LASER PHYSICS; vol. 19; issue 2; pp. 176-184; year: 2009

Abstract: The nondiffusive contribution to the coherent backscattering intensity is calculated for the media with relatively large particles (size a is greater than wavelength lambda). The results are in good agreement with the experimental data at the wings of the angular spectrum of the coherent backscattering. The shape of the backscattering peak is analyzed for strongly absorbing media. The correlation function of the intensity fluctuations is calculated for the scattering by Brownian particles at relatively large time shifts.

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Fragmentation energy shift of giant nuclear resonances

Tulupov, BA; Urin, MH

PHYSICS OF ATOMIC NUCLEI; vol. 72; issue 4; pp. 737-739; year: 2009

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On the incompleteness of the Unruh fermion modes in the Minkowski space

Fedotov, AM; Narozhny, NB; Mur, VD; Gelfer, EG

JETP LETTERS; vol. 89; issue 8; pp. 385-389; year: 2009

Abstract: It has been shown that boost modes of two-dimensional fermions on a light cone are expressed in terms of the Dirac delta function of a complex argument. Therefore, the decomposition of integrals over the entire range of the boost parameter into parts is inapplicable and the Unruh quantization is valid only in the double Rindler wedge, rather than in the entire Minkowski space. This means that the Unruh "effect" is absent for any statistics of particles. Thus, both the theoretical predictions and numerous proposals of experiments based on the assumption of the existence of this effect are unfounded.

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Multiphoton ionization of atoms and ions by high-intensity X-ray lasers

Popruzhenko, SB; Mur, VD; Popov, VS; Bauer, D

JOURNAL OF EXPERIMENTAL AND THEORETICAL PHYSICS; vol. 108; issue 6; pp. 947-962; year: 2009

Abstract: Coulomb corrections to the action function and rate of multiphoton ionization of atoms and ions in a strong linearly polarized electromagnetic field are calculated for high values of the Keldysh adiabaticity parameter. The Coulomb corrections significantly increase the ionization rate for atoms (by several orders of magnitude). An interpolation formula proposed for ionization rate is valid for arbitrary values of the adiabaticity parameter. The high accuracy of the formula is confirmed by comparison with the results of numerical calculations. The general case of elliptic polarization of laser radiation is also considered.

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Nonlocal form of quantum off-shell kinetic equation

Ivanov, YB; Voskresensky, DN

PHYSICS OF ATOMIC NUCLEI; vol. 72; issue 7; pp. 1168-1179; year: 2009

Abstract: A new nonlocal form of the off-shell kinetic equation is derived. While being equivalent to the Kadanoff-Baym and Botermans-Malfliet formulations in the range of formal applicability, it has certain advantages beyond this range. It possessesmore accurate conservation laws for Noether quantities than those in the Botermans-Malfliet formulation. At the same time the nonlocal form, similarly to the Botermans-Malfliet one, allows application of the test-particle method for its numerical solution, which makes it practical for simulations of heavy-ion collisions. The physical meaning of the time-space nonlocality is clarified.

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Long-range correlations of the polarized-light intensity in disordered samples

Gorodnichev, EE; Kuzovlev, AI; Rogozkin, DB

JETP LETTERS; vol. 89; issue 11; pp. 547; year: 2009

Abstract: The spatial correlation function of intensity fluctuations in a speckle formed by polarized light multiply scattered in a disordered sample has been calculated. The dependence of the long-range spatial correlations on the polarization state of incident light and the depolarizing properties of the medium has been determined for the cases of transmission and reflection.

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Capture into rydberg states and momentum distributions of ionized electrons

Shvetsov-Shilovski, NI; Goreslavski, SP; Popruzhenko, SV; Becker, W

LASER PHYSICS; vol. 19; issue 8; pp. 1550; year: 2009

Abstract: The yield of neutral excited atoms and low-energy photoelectrons generated by the electron dynamics in the combined Coulomb and laser field after tunneling is investigated. We present results of Monte-Carlo simulations built on the two-step semiclassical model, as well as analytic estimates and scaling relations for the population trapping into the Rydberg states. It is shown that mainly those electrons are captured into bound states of the neutral atom that due to their initial conditions (i) have moderate drift momentum imparted by the laser field and (ii) avoid strong interaction ("hard" collision) with the ion. In addition, it is demonstrated that the channel of capture, when accounted for in semiclassical calculations, has a pronounced effect on the momentum distribution of electrons with small positive energy. For the parameters that we investigated its presence leads to a dip at zero momentum in the longitudinal momentum distribution of the ionized electrons.

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Hydrodynamical description of first-order phase transitions: Analytical treatment and numerical modeling

Skokov, VV; Voskresensky, DN

NUCLEAR PHYSICS A; vol. 828; issue 3-4; pp. 401; year: 2009

Abstract: Solutions of hydrodynamical equations are presented for an equation of state allowing for a first-order phase transition. The numerical analysis is supplemented by analytical treatment provided the system is close to the critical point. The processes of growth and dissolution of seeds of various sizes and shapes in meta-stable phases (like super-cooled vapor and super-heated liquid) are studied, as well as the dynamics of unstable modes in the spinodal region. We show that initially nonspherical seeds acquire spherical shape with passage of time. Applications to the description of the first-order phase transitions in nuclear systems. such as the nuclear gas-liquid transition occurring in low energy heavy-ion collisions and the hadron-quark transition in the high energy heavy-ion collisions are discussed. In both cases we point out the important role played by effects of viscosity and surface tension. It is shown that fluctuations dissolve and grow as if the fluid were effectively very viscous. Even in the spinodal region seeds may grow slowly due to viscosity and critical slowing down. This prevents the enhancement of fluctuations in the near-critical region, which is frequently considered as a signal of the critical point in heavy-ion collisions.

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Dispersion and attenuation of surface acoustic waves of shear horizontal polarization on a free surface of a hexagonal crystal with a structurally damaged isotropic surface layer

Kosachev, VV; Gandurin, YN; Murav'ev, SE

PHYSICS OF THE LIQUID STATE; vol. 51; issue 9; pp. 1941; year: 2009

Abstract: The phase velocity dispersion and the inverse attenuation length of surface acoustic waves of shear horizontal polarization propagating along a free flat (smooth) surface of a hexagonal crystal (Z cut) in the presence of a thin (compared to the wavelength) structurally damaged surface layer are found in the analytical form. It is shown that, in the long-wavelength limit (the wavelength is large compared to the characteristic size of layer inhomogeneities), which is of the greatest interest to experimenters, the change in the phase velocity dispersion and the change in the inverse attenuation length are proportional to the third and sixth powers of the wave frequency, respectively. The inverse attenuation length is numerically calculated.

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Hydrodynamical description of a hadron-quark first-order phase transition

Skokov, VV; Voskresensky, DN

JETP LETTERS; vol. 90; issue 4; pp. 223; year: 2009

Abstract: Solutions of hydrodynamical equations are presented for the equation of state of the Van der Waals type allowing for a first-order phase transition. As an example we consider the hadron-quark phase transition in heavy-ion collisions. It is shown that fluctuations dissolve and grow as if the fluid is effectively very viscous. In the vicinity of the critical point even in spinodal region seeds are growing slowly due to viscosity, surface tension and critical slowing down. These non-equilibrium effects prevent enhancement of fluctuations in the near-critical region, which in thermodynamical approach is frequently considered as a signal of the critical endpoint in heavy-ion collisions.

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Strong field ionization by ultrashort laser pulses: Application of the Keldysh theory

Karnakov, BM; Mur, VD; Popruzhenko, SV; Popov, VS

PHYSICS LETTERS A; vol. 374; issue 2; pp. 386; year: 2009

Abstract: Analytical expressions and numerical results describing ionization of atoms by intense linearly polarized ultrashort laser pulses are obtained in the frame of the Keldysh approach. Photoelectron spectra and total ionization probabilities are presented for several analytical models of a single-cycle laser pulse. In particular, strong left-right asymmetry of the spectra is shown for the case of odd pulses.

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Magnetic-impurity states of electron in quantum well

Andreev, SP; Pavlova, TV

17th International Conference on Electronic Properties of Two-Dimensional Systems

JUL 15-20, 2007

Genoa, ITALY

PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES; vol. 40; issue 5; pp. 1377; year: 2008

Abstract: A spectrum equation is obtained for the problem of determining the ground state of an electron in an attractive potential with a finite radius located in a quantum well situated in a perpendicular magnetic field H. The solution of this equation is expressed by the parameters of low-energy scattering at H = 0. The expressions describing the diamagnetic and antidiamagnetic shifts from the quantum-dimensional spectrum boundary are found in the limiting cases of narrow and wide quantum wells. The criterion of electron state existence in an impurity potential located at an arbitrary distance from the center of a 2D structure is specified.

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Hydrogenic impurity states in semiconducting nanostructures with anisotropic effective mass

Andreev, SP; Pavlova, TV

17th International Conference on Electronic Properties of Two-Dimensional Systems

JUL 15-20, 2007

Genoa, ITALY

PHYSICA E-LOW-DIMENSIONAL SYSTEMS & NANOSTRUCTURES; vol. 40; issue 5; pp. 1551; year: 2008

Abstract: A hydrogenic impurity located in a semiconducting nanostructure with anisotropic effective mass of carriers m* = (m(perpendicular to), m(perpendicular to), m(parallel to)} is investigated with variation of the impurity position taken into account. A binding energy and deformation of the impurity are analyzed as a function of the layer thickness and impurity position in 2D structures with different effective mass of carriers. The results obtained for the shallow impurity binding energy are in a good agreement with the theoretical calculations both for bulk semiconductors [W. Kohn, J.H. Luttinger, Phys. Rev. 98 (1955) 915] and 2D semiconductors with isotropic effective mass of electrons [G. Bastard, Phys. Rev. B 24 (1981) 4714]. (C) 2007 Elsevier B.V. All rights reserved.

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Influence of a structurally damaged surface layer of the hexagonal crystal on the dispersion and attenuation of Rayleigh surface acoustic waves

Kosachev, VV; Gandurin, YN

PHYSICS OF THE LIQUID STATE; vol. 50; issue 4; pp. 785; year: 2008

Abstract: Analytical expressions for the dispersion of the phase velocity and the inverse attenuation length of Rayleigh waves are derived with allowance made for a thin (as compared to the length of the surface wave) isotropic damaged surface layer that is contiguous with vacuum and located on the surface of a hexagonal crystal with the sixfold axis perpendicular to the surface. It is demonstrated that, in the limit of long wavelengths (as compared to the characteristic inhomogeneity size), which is of greatest interest for experimenters, the change in the dispersion of the phase velocity of Rayleigh waves is proportional to the second power of the frequency, whereas the inverse attenuation length of Rayleigh waves is proportional to the fifth power of the frequency. The inverse attenuation length of the Rayleigh wave is calculated numerically. The calculation method previously proposed by one of the authors (Kosachev, 1998) is generalized to the case of an isotropic damaged layer on an anisotropic (hexagonal) substrate.

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Radiation of a nonrelativistic particle during its finite motion in a central field

Karnakov, BM; Korneev, PA; Popruzhenko, SV

JOURNAL OF EXPERIMENTAL AND THEORETICAL PHYSICS; vol. 106; issue 4; pp. 650; year: 2008

Abstract: The spectrum and expressions for the intensity of dipole radiation lines are obtained for a classical nonrelativistic charged particle that executes a finite aperiodic motion in an arbitrary central field along a non- closed tntiectory. It is shown that, in this case of a conditionally periodic motion, the radiaton spectrum consists of two series of equally spaced lines. It is pointed out that, according to the correspondence principle, the rise of two such series in the classical theory corresponds to the well-known selection rule vertical bar Delta l vertical bar = 1 for the dipole radiation in a central field in quantum theory, where I is the orbital angular momentum of the particle. The results obtained can be applied to the description of the radiation and the absorption of a classical collisionless electron plasma in nanoparticles irradiated by an intense laser field. As an example, the rate of collisionless absorption of electromagnetic wave energy in equilibrium isotropic nanoplasma is calculated.

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Coherent backscattering of polarized light from a turbid medium

Gorodnichev, EE; Kuzovlev, AI; Rogozkin, DB

JOURNAL OF EXPERIMENTAL AND THEORETICAL PHYSICS; vol. 106; issue 4; pp. 731; year: 2008

Abstract: Approximate analytical expressions for the intensities of the polarized components of light reflected from a disordered medium with larcye discrete particles (larger than the wavelength) have been derived with the use of the method of decoupling of the vector transfer equation that is based on separate treatment of basic and additional polarization modes. The results obtained provide the relation between the peak shape in the angular distribution of the backscattered radiation with a given polarization and the optical characteristics of the medium and are in good agreement with experimental data and numerical calculations.

 

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Diffusion of electrons scattered by short-range impurities in a quantizing magnetic field

Andreev, SP; Pavlova, TV

JOURNAL OF EXPERIMENTAL AND THEORETICAL PHYSICS; vol. 106; issue 4; pp. 788; year: 2008

Abstract: Formulas for transverse diffusion and conductivity in a semiconductor are obtained for electrons scattered by neutral impurities in a quantizing magnetic field. The formulas are valid for an impurity potential of arbitrary depth. Based on Kubo's theory [1], calculations are performed using electron wavefunctions of the problem of single-impurity scattering in a magnetic field [2]. The poles of the scattering amplitude correctly determine electron eigenstates and magnetic impurity states. As a result, an exact expression is found for the dependence of transverse diffusion coefficient D-perpendicular to on longitudinal electron energy epsilon due to scattering by short-range (neutral) impurities. The behavior of D-perpendicular to(epsilon) is examined over an interval of magnetic field strength for several values of impurity potential depth. The experimental observability of diffusion and conductivity using IR lasers is discussed.

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Comment on "laser-assisted muon decay''

Narozhny, NB; Fedotov, AM

PHYSICAL REVIEW LETTERS; vol. 100; issue 21; year: 2008

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Coulomb-corrected quantum trajectories in strong-field ionization

Popruzhenko, SV; Paulus, GG; Bauer, D

PHYSICAL REVIEW A; vol. 77; issue 5; year: 2008

Abstract: Nonperturbative analytical quantum treatments of strong-field laser-atom interaction are essentially based on the assumption that binding forces are negligible once the electron is emitted because the further dynamics are considered as being dominated by the laser field. In this work we introduce a Coulomb-corrected strong-field theory of photoionization based on quantum trajectories and show how binding forces lead to strong qualitative effects in above-threshold ionization of atoms. We examine the theory by comparing experimental data for elliptically polarized laser fields and results from the ab initio solution of the time-dependent Schrodinger equation with our theoretical predictions. The comparison shows good quantitative agreement with the ab initio results and reasonable agreement with the data. For ground states with nonzero angular momentum we show a strong circular dichroism in the high-energy (rescattering) part of photoelectron spectra.

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Harmonic emission from cluster nanoplasmas subject to intense short laser pulses

Popruzhenko, SV; Kundu, M; Zaretsky, DF; Bauer, D

PHYSICAL REVIEW A; vol. 77; issue 6; year: 2008

Abstract: Harmonic emission from cluster nanoplasmas subject to short intense infrared laser pulses is studied. In a previous publication [M. Kundu , Phys. Rev. A 76, 033201 (2007)] we reported particle-in-cell simulation results showing resonant enhancements of low-order harmonics when the Mie plasma frequency of the ionizing and expanding cluster resonates with the respective harmonic frequency. Simultaneously we found that high-order harmonics were barely present in the spectrum, even at high intensities. The current paper is focused on the analytical modeling of the process. We show that dynamical stochasticity owing to nonlinear resonance inhibits the emission of high-order harmonics.

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Ellipticity effects and the contributions of long orbits in nonsequential double ionization of atoms

Shvetsov-Shilovski, NI; Goreslavski, SP; Popruzhenko, SV; Becker, W

PHYSICAL REVIEW A; vol. 77; issue 6; year: 2008

Abstract: Using a semiclassical model based on tunneling, electron kinematics in the laser field, and phase space volume, we evaluate the ion and electron momentum distributions in nonsequential double ionization of a model atom by an elliptically polarized laser field. For ellipticities exceeding approximately 0.3, we find that the shortest quantum orbit (having the shortest travel time) no longer dominates the double-ionization rate, in contrast to the case of linear polarization. Simultaneously we observe significant violations of symmetry patterns in the ion-momentum distributions and the electron-electron momentum correlations, compared with the case of linear polarization. These violations are very sensitive to the laser pulse duration because of the absence of the late returns for very short pulses. Some of these qualitative effects in the photoelectron distributions should be experimentally detectable. Observation would verify the significance of the late returns and the underlying quantum-orbit concept.

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Neutrino emission due to Cooper-pair recombination in neutron stars reexamined

Kolomeitsev, EE; Voskresensky, DN

PHYSICAL REVIEW C; vol. 77; issue 6; year: 2008

Abstract: Neutrino emission in processes of breaking and formation of neutron and proton Cooper pairs is calculated within the Larkin-Migdal-Leggett approach for a superfluid Fermi liquid. We demonstrate explicitly that the Fermi-liquid renormalization respects the Ward identity and ensures the weak vector-current conservation. The systematic expansion of the emissivities for small temperatures and nucleon Fermi velocity v(F,i),i=n,p, is performed. Both neutron and proton processes are mainly controlled by the axial-vector current contributions, which are not strongly changed in the superfluid matter. Thus, compared to earlier calculations, the total emissivity of processes on neutrons paired in the 1S(0) state is suppressed by a factor of similar or equal to(0.9-1.2)v(F,n)(2). A similar suppression factor (similar to v(F,p)(2)) arises for processes on protons.

 

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Gamow-Teller strength distributions for beta beta-decaying nuclei within continuum QRPA

Igashov, SY; Rodin, VA; Urin, MH; Faessler, A

PHYSICS OF ATOMIC NUCLEI; vol. 71; issue 7; pp. 1267; year: 2008

Abstract: A version of the pn continuum QRPA is outlined and applied to describe the Gamow-Teller strength distributions for beta beta-decaying open-shell nuclei. The calculation results obtained for the pairs of nuclei Cd-116-Sn and Te-130-Xe are compared with available experimental data.

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Coulomb correction to the ionization rate of atoms in high-frequency intense laser fields

Popruzhenko, SV; Mur, VD; Popov, VS

PHYSICS LETTERS A; vol. 372; issue 31; pp. 5167; year: 2008

Abstract: A Coulomb correction to the rate of multiphoton ionization of atoms and positive ions in intense high-frequency laser fields is found using the imaginary time method for a subbarrier trajectory and Kapitza method for description of motion in a rapidly oscillating field. The obtained results cover the domain of parameters opposite to the well-studied low-frequency tunneling limit. We show that the Coulomb correction enhances the ionization rate up to several orders in magnitude. Application of the obtained results for description of multiphoton ionization in intense ultraviolet laser pulses is briefly discussed.

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Strong field approximation for systems with Coulomb interaction

Popruzhenko, SV; Bauer, D

JOURNAL OF MODERN OPTICS; vol. 55; issue 16; pp. 2573; year: 2008

Abstract: A theory describing above-threshold ionization of atoms and ions in a strong electromagnetic field is presented. It is based on the widely known strong field approximation and incorporates the Coulomb interaction between the photoelectron and the nucleus using the method of complex classical trajectories. A central result of the theory is the Coulomb-corrected ionization amplitude whose evaluation requires little extra numerical effort. By comparing our predictions with the results of ab initio numerical solutions for two examples we show that the new theory provides a significant improvement of the Coulomb-free strong field approximation. For the case of above-threshold ionization in elliptically polarized fields a comparison with available experimental data is also presented.

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Energy absorption and emission of harmonics by clusters subject to intense short laser pulses

Popruzhenko, SV; Zaretsky, DF; Bauer, D

LASER PHYSICS LETTERS; vol. 5; issue 9; pp. 631; year: 2008

Abstract: Experimental and theoretical achievements in studies of atomic and metal clusters interacting with short intense infrared laser pulses are reviewed. The focus is made on the theoretical concepts describing the energy transfer from the laser field to the cluster nanoplasma and emission of laser harmonics from it. Both effects are considered assuming the collisionless regime, where the interaction of nanoplasma electrons with the self-consistent field dominates the individual collisions. The pivotal role of nonlinear resonances is underlined and described in detail. Possible ways for a further development of the theory and experimental perspectives are briefly discussed.

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Recollision-induced plasmon excitation in strong laser fields

Ruggenthaler, M; Popruzhenko, SV; Bauer, D

PHYSICAL REVIEW A; vol. 78; issue 3; year: 2008

Abstract: Recolliding electrons are responsible for many of the interesting phenomena observed in the interaction of strong laser fields with atoms and molecules. We show that in multielectron targets such as C-60 an important recollision pathway opens up: the returning electron may excite collective modes even if the laser frequency is far off-resonant. We formulate a simple analytical theory which predicts that the recollision-induced excitation of collective modes should dominate over the "usual" harmonic generation yield at 800 nm wavelength. In this case the tomographic imaging of complex multielectron systems may be obscured. We employ a time-dependent density functional model of C-60 and show that with increasing laser wavelength the dynamics becomes more and more single-active-electron-like, suggesting that long wavelengths are to be preferred for imaging purposes.

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Direct-decay properties of giant resonances

Urin, MH

NUCLEAR PHYSICS A; vol. 811; issue 1-2; pp. 107; year: 2008

Abstract: A semi-microscopic approach, based on the continuum-RPA method and a phenomenological treatment of the spreading effect, is outlined and applied to describe direct-decay properties of a few isovector giant resonances. The ability of the approach to describe giant-resonance gross properties is also checked.

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Thermodynamics of resonances and blurred particles

Voskresensky, DN

NUCLEAR PHYSICS A; vol. 812; pp. 158; year: 2008

Abstract: Exact and approximate expressions for thermodynamic characteristics of heated matter, which consists of particles with finite mass-widths, are constructed. They are expressed in terms of Fermi/Bose distributions and spectral functions, rather than in terms of more complicated combinations between real and imaginary parts of the self-energies of different particle species. Therefore thermodynamically consistent approximate treatment of systems of particles with finite mass-widths can be performed, provided spectral functions of particle species are known. Approximation of the free resonance gas at low densities is studied. Simple ansatz for the energy dependence of the spectral function is suggested that allows to fulfill thermodynamical consistency conditions. On examples it is shown that a simple description of dense systems of interacting particle species can be constructed, provided some species can be treated in the quasiparticle approximation and others as particles with widths. The interaction affects quasiparticle contributions, whereas particles with widths can be treated as free. Example is considered of a hot gas of heavy fermions strongly interacting with light bosons, both species with zero chemical potentials. The density of bluffed fermions is dramatically increased for high temperatures compared to the standard Boltzmann value. The system consists of boson quasiparticles (with effective masses) interacting with fermion-antifermion blurs. In thermodynamical values interaction terms partially compensate each other. Thereby, in case of a very strong coupling between species thermodynamical quantities of the system, like the energy, pressure and entropy, prove to be such as for the quasi-ideal gas mixture of quasi-free fermion blurs and quasi-free bosons.

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Strong Field Ionization Rate for Arbitrary Laser Frequencies

Popruzhenko, SV; Mur, VD; Popov, VS; Bauer, D

PHYSICAL REVIEW LETTERS; vol. 101; issue 19; year: 2008

Abstract: A simple, analytical, nonrelativistic ionization rate formula for atoms and positive ions in intense ultraviolet and x-ray electromagnetic fields is derived. The rate is valid at arbitrary values of the Keldysh parameter and confirmed by results from ab initio numerical solutions of the single active electron, time-dependent Schrodinger equation. The proposed rate is particularly relevant for experiments employing the new free electron laser sources.

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Relativistic mean-field model with scaled hadron masses and couplings

Khvorostukhin, AS; Toneev, VD; Voskresensky, DN

NUCLEAR PHYSICS A; vol. 813; issue 3-4; pp. 313; year: 2008

Abstract: Here we continue to elaborate properties of the relativistic mean-field based model (SHMC) proposed in [A.S. Khvorostukhin, V.D. Toneev. D.N. Voskresensky, Nucl. Phys. A 791 (2007) 180] where hadron masses and coupling constants depend on the sigma-meson field. The validity of approximations used in this reference is discussed. We additionally incorporate contribution of meson excitations to the equations of motion. We also estimate the effects of the particle width. It is demonstrated that the inclusion of the baryon-baryon hole and baryon-antibaryon loop terms, if performed perturbatively, destroys the consistency of the model.

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On the keldysh ionization theory for ultrashort laser pulses

Karnakov, BM; Mur, VD; Popov, VS

JETP LETTERS; vol. 88; issue 7; pp. 423-427; year: 2008

Abstract: A closed analytical expression is obtained for the momentum distribution of photoelectrons from the ionization of atoms or ions by an ultrashort laser pulse. This formula is applied to analyze some models of electromagnetic pulses and the interference effect in the ionization probability.

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Damping mechanisms of high-lying single-particle states in Nb-91

Van der Molen, HKT; Akimune, H; van den Berg, AM; Daito, I; Fujimura, H; Fujita, Y; Fujiwara, M; Harakeh, MN; Hunyadi, M; Ihara, F; Inomata, T; Ishibashi, K; Janecke, J; Kalantar-Nayestanaki, N; Laurent, H; Lhenry, I; O'Donnell, TW; Rodin, VA; Tamii, A; Toyokawa, H; Urin, MH; Yoshida, H; Yosoi, M

PHYSICAL REVIEW C; vol. 75; issue 1; year: 2007

Abstract: Decay by proton emission from high-lying states in Nb-91, populated in the Zr-90(alpha,t) reaction at E-alpha=180 MeV, has been investigated. Decay to the ground state and semidirect decay to the low-lying (2(+),5(-), and 3(-)) phonon states in Zr-90 were observed. It was found that these phonon states play an important role in the damping process of the single-particle states. An optical-model coupled-channel approach was used successfully to describe the direct and semidirect parts of the decay.

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Structural materials for fusion power reactors - the RF R & D activities

Chernov, VM; Leonteva-Smirnova, MV; Potapenko, MM; Budylkin, NI; Devyatko, YN; Ioltoukhovskiy, AG; Mironova, EG; Shikov, AK

NUCLEAR FUSION; vol. 47; issue 8; pp. 839-848; year: 2007

Abstract: Recent progress in the RF low activation structural materials R&D road map towards DEMO via the FBR tests (BOR-60, BN-600, BN-800) and the TBM tests in ITER is overviewed. The properties of the RAFMS RUSFER-EK-181 (Fe-12Cr-2W-Ta-V-B-C) and the V-4Ti-4Cr alloys are presented. The next important steps include further studies on the influence of high dose and high-temperature irradiation on the properties of base structural materials and joints. Activation, transmutation and radiation damage of the materials in BN-600 and DEMO-RF (Kurchatov Institute project) neutron spectra are calculated. The results of the application of the internal friction (ultrasonic) non-destructive method to research the DBTT are in good agreement with the results of the destructive impact method. The important influence of boron on the heat resistance of materials and the He concentration level under irradiation are calculated. The new special regimes of the heat treatments of the alloys are suggested to widen the temperature windows of the applications. The results of the BOR-60 examinations of RUSFER-EK-181 (irradiation temperature 320-340 degrees C and doses up to 15 dpa) are presented. The BN-600 projects for the high dose and high-temperature irradiation tests of manufactured alloys are presented.

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Generation of harmonics by a focused laser beam in the vacuum

Fedotov, AM; Narozhny, NB

PHYSICS LETTERS A; vol. 362; issue 1; pp. 1-5; year: 2007

Abstract: We consider generation of odd harmonics by a super strong focused laser beam in the vacuum. The process occurs due to the plural light-by-light scattering effect. In the leading order of perturbation theory, generation of (2k + 1)th harmonic is described by a loop diagram with (2k + 2) external incoming, and two outgoing legs. A frequency of the beam is assumed to be much smaller than the Compton frequency, so that the approximation of a constant uniform electromagnetic field is valid locally. Analytical expressions for angular distribution of generated photons, as well as for their total emission rate are obtained in the leading order of perturbation theory. Influence of higher-order diagrams is studied numerically using the formalism of Intense Field QED. It is shown that the process may become observable for the beam intensity of the order of 10(27) W/cm(2). (c) 2006 Elsevier B.V. All rights reserved.

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On the dynamical Casimir effect in a one-dimensional contracting cavity

Fedotov, AM; Narozhny, NB; Petrosyan, AN; Lozovik, YE

LASER PHYSICS; vol. 17; issue 4; pp. 310-315; year: 2007

Abstract: The dynamical Casimir effect is analyzed in the framework of the S-matrix formulation for a one-dimensional cavity that exhibits contraction at a constant rate over a finite time interval. The exact solution to the problem is presented. It is demonstrated that the efficiency of the creation of pairs nonmonotonically depends on the contraction time. This is due to the fact that the particles are only created at the moments corresponding to the acceleration and stopping of the moving boundary, so that the contributions of these processes on the number of the created particles interfere with each other. The parameters that correspond to the optimal creation of pairs and the stability of a vacuum are presented. The effect of the finiteness of the cavity-boundary acceleration on the results obtained is studied.

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Multiple scattering of polarized light in a turbid medium

Gorodnichev, EE; Kuzovlev, AI; Rogozkin, DB

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 104; pp. 319-341; year: 2007

Abstract: It is shown that multiple scattering of polarized light in a turbid medium can be represented as independent propagation of three basic modes: intensity and linearly and circularly polarized modes. Weak interaction between the basic modes can be described by perturbation theory and gives rise to "overtones" (additional polarization modes). Transport equations for the basic and additional modes are derived from a vector radiative transfer equation. Analytical solutions to these equations are found in the practically important cases of diffusive light propagation and small-angle multiple scattering. The results obtained are in good agreement with experimental and numerical results and provide an explanation for the experimentally observed difference in depolarization between linearly and circularly polarized waves.

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Equation of state for hot and dense matter: sigma-omega-p model with scaled hadron masses and couplings

Khvorostukhin, AS; Toneev, VD; Voskresensky, DN

NUCLEAR PHYSICS A; vol. 791; issue 1-2; pp. 180-221; year: 2007

Abstract: The proposed earlier relativistic mean-field model with hadron masses and coupling constants depending on the (sigma-meson field is generalized to finite temperatures. Within this approach we simulate the in-medium behavior of the hadron masses motivated by the Brown-Rho scaling. The high-lying baryon resonances and boson excitations as well as excitations of the sigma, omega and rho fields interacting via mean fields are incorporated into this scheme. Thermodynamic properties of hot and dense hadronic matter are elaborated with the constructed equation of state. Even at zero baryon density, effective masses of sigma-omega-rho-N excitations abruptly drop down for T greater than or similar to 170 MeV and reach zero at a critical temperature T = T-c sigma similar to 2 10 MeV. Below T-c sigma (at T similar to 190 MeV) the specific heat gets a peak like at crossover. We demonstrate that our EoS can be matched with that computed on the lattice for high temperatures provided the baryon resonance couplings with nucleon are partially suppressed. In this case the quark liquid would masquerade as the hadron one. The model is applied to the description of heavy ion collisions in a broad collision energy range. It might be especially helpful for studying phase diagram in the region near possible phase transitions. (c) 2007 Elsevier B.V. All rights reserved.

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Third-harmonic generation in a vacuum at the focus of a high-intensity laser beam

Narozhny, NB; Fedotov, AM

LASER PHYSICS; vol. 17; issue 4; pp. 350-357; year: 2007

Abstract: A new physical effect lying in the harmonic generation by a focused high-intensity (I similar to 10(27) W/cm(2)) laser beam in a vacuum is predicted. The probability for the third-harmonic generation is calculated for a specific model of a monochromatic laser beam (symmetric beam) with the optical frequency.

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On the inclusion of the Coulomb interaction in the theory of multiphoton ionization

Popov, VS; Mur, VD; Popruzhenko, SV

JETP LETTERS; vol. 85; issue 5; pp. 223-226; year: 2007

Abstract: The Coulomb correction to the rate of multiphoton ionization of atoms and ions by intense laser radiation is derived for large Keldysh adiabaticity parameters using the imaginary time method. This correction increases the ionization rate by several orders of magnitude.

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Two-dimensional streaking: complete characterization of an arbitrarily polarized few-cycle laser pulse using a stereodetector technique

Popruzhenko, SV; Shvetsov-Shilovski, NI; Goreslavski, SP; Becker, W; Paulus, GG

OP CS LETTERS; vol. 32; pp. 1372-1374; year: 2007

Abstract: We discuss the feasibility of measuring the temporal variation of the electric-field strength of a few-cycle laser pulse with arbitrary polarization using the attosecond streaking method. It is shown that a full characterization of the field requires measuring the photoelectron momenta in two opposite directions in the laser polarization plane for various delays of the extreme ultraviolet burst with respect to the probed laser pulse. (c) 2007 Optical Society of America.

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Nonlinear helicon-phonon resonance in bismuth

Skobov, VG; Chernov, AS

PHYSICS OF THE LID STATE; vol. 49; issue 6; pp. 1064-1066; year: 2007

Abstract: The effect of nonlinearity on the helicon-phonon resonance in bismuth is considered. It is shown that, in the nonlinear regime, the frequency range in which resonance is possible expands and the resonance curve changes in shape: the lower boundary of this range decreases, and the resonance maximum of the acoustic wave damping becomes higher and narrower.

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Relativistic generalization of the Keldysh ionization theory

Karnakov, BM; Mur, VD; Popov, VS

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 105; pp. 292-305; year: 2007

Abstract: A relativistic theory of tunneling is developed. Ionization of atoms and ions by a constant crossed field and an ultrashort laser pulse, ionization probability as a function of the adiabaticity parameter and the pulse shape, the limit of the Keldysh nonrelativistic ionization theory, and the photoelectron momentum spectrum are considered. In calculations, the imaginary time method is used.

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Harmonic generation from laser-irradiated clusters

Kundu, M; Popruzhenko, SV; Bauer, D

PHYSICAL REVIEW A; vol. 76; year: 2007

Abstract: The harmonic emission from cluster nanoplasmas subject to short, intense infrared laser pulses is analyzed by means of particle-in-cell simulations. A pronounced resonant enhancement of the low-order harmonic yields is found when the Mie plasma frequency of the ionizing and expanding cluster resonates with the respective harmonic frequency. We show that a strong, nonlinear resonant coupling of the cluster electrons with the laser field inhibits coherent electron motion, suppressing the emitted radiation and restricting the spectrum to only low-order harmonics. A pump-probe scheme is suggested to monitor the ionization dynamics of the expanding clusters.

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Reconstruction of an arbitrarily polarized few-cycle laser pulse by two-dimensional streaking

Shvetsov-Shilovski, NI; Goreslavski, SP; Popruzhenko, SV; Becker, W; Paulus, GG

LASER PHYSICS LETTERS; vol. 4; pp. 726-733; year: 2007

Abstract: ne application of the streaking principle for the reconstruction of the temporal evolution of the electric field of a few-cycle laser pulse with arbitrary polarization is discussed. A full characterization of the field can be achieved by measuring the photoelectron energy-angular distribution in the polarization plane for various delays of the attosecond XUV burst with respect to the probed laser pulse. A simplified realization of the procedure, which is unable to determine the sign of the ellipticity, requires a measurement of the photoelectron momentum in two opposite directions along an arbitrary axis. The reconstructed field is robust against the detailed shape of the angular dependence, as well as details of the theoretical model employed in the reconstruction. An error analysis shows that, for moderate intensities of the probed pulse, high accuracy of the reconstruction can be achieved.

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Collisionless absorption of intense laser radiation in nanoplastna

Zaretsky, DF; Korneev, PA; Popruzhenko, SV

QUANTUM ELECTRONICS; vol. 37; pp. 565-574; year: 2007

Abstract: The rate of linear collisionless absorption of an electromagnetic radiation in a nanoplasma - classical electron gas localised in a heated ionised nanosystem (thin film or cluster) irradiated by an intense femtosecond laser pulse - is calculated. The absorption is caused by the inelastic electron scattering from the self-consistent potential of the system in the presence of a laser field. The effect proves to be appreciable because of a small size of the systems. General expressions are obtained for the absorption rate as a function of the parameters of the single-particle self-consistent potential and electron distribution function in the regime linear in field. For the simplest cases, where the self-consistent field is created by an infinitely deep well or an infinite charged plane, closed analytic expressions are obtained for the absorption rate. Estimates presented in the paper demonstrate that, over a wide range of the parameters of laser pulses and nanostructures, the collisionless mechanism of heating electron subsystem can be dominant. The possibility of experimental observation of the collisionless absorption of intense laser radiation in nanoplasma is also discussed.

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Magnetic-impurity states of electron in two-dimensional semiconductor structures

Andreev, SP; Pavlova, TV

LASER PHYSICS; vol. 16; issue 6; pp. 998-1004; year: 2006

Abstract: Electron states on an attractive center of small-radius r(c) << l (l = root c (h) over bar /eH is the magnetic length) located in a two-dimensional structure are investigated in a uniform magnetic field H applied perpendicularly to the structure surface. The spectrum of magnetic-impurity (MI) particle states with an arbitrary moment projection on the direction H for Landau bands 0 <= N < l(2)/r(c)(2) is derived in the approximation that mixing of Landau levels is weak. The dependence of the electron energy states on magnetic field, the layer thickness, and the impurity position are studied. It is shown that dimension lowering leads to a qualitatively different spectrum of MI states compared to the three-dimensional case [1]. A comparison of the obtained binding energy of the D- center with experimental data is performed.

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Asymmetric neutrino propagation in newly born magnetized strange stars; GRB and kicks

Berdermann, J; Blaschke, D; Grigorian, H; Voskresensky, DN; ED Faessler, A

INTERNATIONAL WORKSHOP ON NUCLEAR PHYSICS 27TH COURSE: NEUTRINOS IN COSMOLOGY, IN ASTRO, PAR CLE AND NUCLEAR PHYSICS; vol. 57; issue 1; pp. 334-342; year: 2006

Abstract: We consider the early cooling evolution of strongly magnetized strange stars in a color-flavor-locked phase with high gap Delta greater than or similar to 100 MeV. We demonstrate how this model may explain the main features of the gamma-ray burst phenomena and also yield a strong star kick. The mechanism is based on beaming of neutrino emission along the magnetic vortex lines. We show that for sufficiently high initial temperatures T-0 similar to 30-60 MeV and surface magnetic fields B-s similar to 10(15)-10(17) G, the energy release within the narrow beam is up to 1052 erg with a magnetic field dependent timescale between 10(-2) s (for a smaller magnetic field) and 10 s. The above mechanism together with the parity violation of the neutrino-producing weak interaction processes in a magnetic field allow for the strange star lick. The higher the magnetic field the larger the star kick velocity. These velocities may cover the same range as observed pulsar kick velocities. (c) 2006 Elsevier B.V. All rights reserved.

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Electron-positron pair production by electromagnetic pulses

Bulanov, SS; Narozhny, NB; Mur, VD; Popov, VS

JOURNAL OF EXPERIMENTAL AND THEORETICAL PHYSICS; vol. 102; issue 1; pp. 9-23; year: 2006

Abstract: Electron-positron pair production in vacuum by a single focused laser pulse and by two counter-propagating colliding focused pulses is analyzed. A focused laser pulse is described using a realistic three-dimensional model based on an exact solution of Maxwell's equations. In particular, this model reproduces an important property of focused beams, namely, the existence of two types of waves with a transverse electric or magnetic vector (e- or h-polarized wave, respectively). The dependence of the number of produced pairs on the radiation intensity and focusing parameter is studied. It has been shown that the number of pairs produced in the field of a single e-polarized pulse is many orders of magnitude larger than that for an h-polarized pulse. The pulse-intensity dependence of the number of pairs produced by a single pulse is so sharp that the total energy of pairs produced by the e-polarized pulse with intensity near the intensity I-s = 4.65 x 10(29) W/cm(2) characteristic of QED is comparable with the energy of the pulse itself. This circumstance imposes a natural physical bound on the maximum attainable intensity of a laser pulse. For the case of two colliding circularly polarized pulses, it is shown that pair production becomes experimentally observable when the intensity of each beam is l similar to 10(26) W/cm(2), which is one to two orders of magnitude lower than that for a single pulse.

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The influence of relaxation on the structure and boundary shape of adatom islands on an incommensurable substrate - art. no. 62600Q

Devyatko, YN; Rogozhkin, SV; Fadeev, AV

Micro- and Nanoelectronics 2005; vol. 6260; pp. Q2600-2600; year: 2006

Abstract: The structure of monolayer (adatom island) is investigated with taking into account of relaxation of atoms in a changeless field of substrate, which is incommensurate to the monolayer structure. The influence of relaxation of the structure and shape of adatom island on its orientation in relation to the structure of substrate is shown. It is established that the monolayer structure has a superstructure with periodicity which is inversely proportional to the incommensurability. It is shown that the shape of an island and its orientation in relation to the structure of substrate changes during its growth. The results of calculations are compared to the experiment.

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Dynamical Casimir effect in a one-dimensional uniformly contracting cavity

Fedotov, AM; Lozovik, YE; Narozhny, NB; Petrosyan, AN

PHYSICAL REVIEW A; vol. 74; issue 1; year: 2006

Abstract: We consider the particle creation (the Dynamical Casimir effect) in a uniformly contracting ideal one-dimensional cavity nonperturbatively. The exact expression for the energy spectrum of created particles is obtained and its dependence on parameters of the problem is discussed. Unexpectedly, the number of created particles depends on the duration of the cavity contracting nonmonotonously. This is explained by quantum interference of the events of particle creation which are taking place only at the moments of acceleration and deceleration of a boundary, while stable particle states exist (and thus no particles are created) at the time of contracting.

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On a semimicroscopic description of extremely simple photonuclear reactions involving the excitation of a giant dipole resonance

Gorelik, ML; Urin, MH

PHYSICS OF ATOMIC NUCLEI; vol. 69; issue 2; pp. 219-229; year: 2006

Abstract: A quantitative interpretation of basic properties of a giant dipole resonance is proposed within a semimicroscopic approach relying on the random-phase approximation that takes exactly into account a single-particle continuum and on a phenomenological description of the fragmentation effect. For some magic and semimagic nuclei, the calculated photoabsorption cross sections and cross sections for partial photoneutron "direct + semidirect" reactions in the vicinity of the above resonance are compared with their experimental counterparts.

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Asymmetry of the angular distributions of products of photoneutron direct-semidirect reactions in the region of an isovector giant quadrupole resonance

Gorelik, ML; Tulupov, BA; Urin, MH

PHYSICS OF ATOMIC NUCLEI; vol. 69; issue 4; pp. 598-606; year: 2006

Abstract: A semimicroscopic approach based on the random-phase approximation exactly taking into account a single-particle continuum and oil a phenomenological description of the fragmentation effect is used to describe the basic properties of an isovector giant quadrupole resonance. The same approach is employed to perform a quantitative analysis of the asymmetry in the angular distributions of products of photoneutron "direct + semidirect" reactions in the region Of Such a resonance. The results of the calculations performed for the target nucleus Pb-208 are compared with available experimental data.

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Depolarization of multiply scattered light in transmission through a turbid medium with large particles

Gorodnichev, EE; Kuzovlev, AI; Rogozkin, DB

OP CS COMMUNICA ONS; vol. 260; pp. 30-45; year: 2006

Abstract: An approximate analytical method for solving the vector radiative transfer equation is proposed. The method is based on the assumption that single scattering of light by large-scale inhomogeneities occurs predominantly through small angles. The method is applied to calculate the polarization state of multiply scattered light. The results obtained are discussed for various turbid media. (c) 2005 Elsevier B.V. All rights reserved.

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Transition radiation from an ultrarelativistic particle in an external field at grazing emission angles

Ivliev, SV; Ryazanov, I; Strikhanov, MN

PHYSICS OF ATOMIC NUCLEI; vol. 69; issue 5; pp. 872-875; year: 2006

Abstract: The effect of an external field on the transition radiation from an ultrarelativistic particle is considered at grazing emission angles. The angular and frequency distribution of transition radiation is found. It is shown that the external field substantially increases the angular asymmetry of transition radiation at grazing emission angles.

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Constraints on the high-density nuclear equation of state from the phenomenology of compact stars and heavy-ion collisions

Klahn, T; Blaschke, D; Typel, S; van Dalen, ENE; Faessler, A; Fuchs, C; Gaitanos, T; Grigorian, H; Ho, A; Kolomeitsev, EE; Miller, MC; Ropke, G; Truemper, J; Voskresensky, DN; Weber, F; Wolter, HH

PHYSICAL REVIEW C; vol. 74; issue 3; year: 2006

Abstract: A new scheme for testing nuclear matter equations of state (EoSs) at high densities using constraints from neutron star (NS) phenomenology and a flow data analysis of heavy-ion collisions is suggested. An acceptable EoS shall not allow the direct Urca process to occur in NSs with masses below 1.5M, and also shall not contradict flow and kaon production data of heavy-ion collisions. Compact star constraints include the mass measurements of 2.1 +/- 0.2M (1 sigma level) for PSR J0751+1807 and of 2.0 +/- 0.1M from the innermost stable circular orbit for 4U 1636-536, the baryon mass-gravitational mass relationships from Pulsar B in J0737-3039 and the mass-radius relationships from quasiperiodic brightness oscillations in 4U 0614+09 and from the thermal emission of RX J1856-3754. This scheme is applied to a set of relativistic EoSs which are constrained otherwise from nuclear matter saturation properties. We demonstrate on the given examples that the test scheme due to the quality of the newly emerging astrophysical data leads to useful selection criteria for the high-density behavior of nuclear EoSs.

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On the relativistic generalization of Keldysh ionization theory

Popov, VS; Mur, VD; Karnakov, BM; Pozdnyakov, SG

PHYSICS LETTERS A; vol. 358; issue 1; pp. 21-26; year: 2006

Abstract: Relativistic generalization of the semiclassical theory of tunnel and multiphoton ionization of atoms and ions in the field of a high-intensity electromagnetic wave (Keldysh theory) with linear and elliptic polarizations is developed. The exponential factor in the ionization rate of relativistic bound state is calculated for arbitrary values of the adiabaticity parameter gamma. In the case of low-frequency laser radiation, gamma << 1, the asymptotically exact formula is derived for the ionization rate of atomic s-level, including the Coulomb, spin and adiabatic corrections and the pre-exponential factor. The ionization rate of the ground state of a hydrogen-like atoms (ions) with Z less than or similar to 100 is calculated, depending on laser intensity and ellipticity of radiation. (c) 2006 Elsevier B.V. All rights reserved.

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Relativistic theory of tunnel and multiphoton ionization of atoms in a strong laser field

Popov, VS; Karnakov, BM; Mur, VD; Pozdnyakov, SG

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 102; issue 5; pp. 760-775; year: 2006

Abstract: Relativistic generalization is developed for the semiclassical theory of tunnel and multiphoton ionization of atoms and ions in the field of an intense electromagnetic wave (Keldysh theory). The cases of linear, circular, and elliptic polarizations of radiation are considered. For arbitrary values of the adiabaticity parameter gamma, the exponential factor in the ionization rate for a relativistic bound state is calculated. For low-frequency laser radiation (gamma << 1), an asymptotically exact formula for the tunnel ionization rate for the atomic s level is obtained including the Coulomb, spin, and adiabatic corrections and the preexponential factor. The ionization rate for the ground level of a hydrogen-like atom (ion) with Z less than or similar to 100 is calculated as a function of the laser radiation intensity. The range of applicability is determined for nonrelativistic ionization theory. The imaginary time method is used in the calculations.

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Third harmonic generation by small metal clusters in a dielectric medium

Popruzhenko, SV; Zaretsky, DF; Becker, W

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OP CAL PHYSICS; vol. 39; issue 23; pp. 4933-4943; year: 2006

Abstract: A simple analytical theory which treats the nonlinear properties of cold metal clusters embedded into a homogeneous isotropic dielectric medium is formulated. The theory is applied to the description of third-harmonic generation (THG) by such clusters irradiated by a laser field of moderate intensity. Competition between different mechanisms of THG and possible interference effects are discussed. A comparison with the recent experimental data shows that the size-dependent surface nonlinearity may dominate over the bulk effects only for small clusters with radii below 10 nm.

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On the properties of charge-exchange dipole excitations and the T-> component of a giant dipole resonance in spherical nuclei

Safonov, IV; Gorelik, ML; Urin, MH

PHYSICS OF ATOMIC NUCLEI; vol. 69; issue 3; pp. 403-417; year: 2006

Abstract: Within the semimicroscopic approach based on the random-phase approximation that takes exactly into account a single-particle continuum and on a phenomenological inclusion of the fragmentation effect, it is proposed to describe the strength functions for charge-exchange giant dipole resonances and cross sections for photoabsorption and for partial "direct + semidirect" (gamma,p) reactions in the vicinity of a giant E1 resonance with allowance for the isospin-splitting effect. The results of the calculations performed for some magic and semimagic nuclei without resort to free parameters are compared with available experimental data.

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On direct proton decay of the isovector spin-flip giant monopole resonance

Safonov, IV; Urin, MH

PHYSICS OF ATOMIC NUCLEI; vol. 69; issue 7; pp. 1215-1219; year: 2006

Abstract: A semimicroscopic approach based on both the continuum-RPA method and a phenomenological treatment of the spreading effect is applied to describe the direct proton decay and gross properties of the charge-exchange isovector spin-flip giant monopole resonance. Calculation results are compared with the available experimental data.

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Helicon-phonon resonance in bismuth

Skobov, VG; Chernov, AS

PHYSICS OF THE LID STATE; vol. 48; issue 1; pp. 20-23; year: 2006

Abstract: The possibility of helicon-phonon resonance occurring in a bismuth crystal is demonstrated. This resonance should be observed in the range of short radio waves propagating in a bismuth crystal in a constant magnetic field H aligned parallel to the bisecting axis directed along the normal to the surface of the crystal plate. The resonance is caused by the deformation interaction of holes with an acoustic wave. It is revealed that the helicon-phonon resonance occurs in relatively weak magnetic fields (of the order of several tens of oersteds) under the condition where spatial inhomogeneity of the wave field is immaterial for the electrons but significant for the holes.

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Finite size effects on kaonic "pasta" structures

Maruyama, T; Tatsumi, T; Voskresensky, DN; Tanigawa, T; Endo, T; Chiba, S

PHYSICAL REVIEW C; vol. 73; issue 3; year: 2006

Abstract: Nonuniform structures of mixed phases at the first-order phase transition to charged kaon condensation are studied using a density functional theory within the relativistic mean-field model. Including electric field effects and applying the Gibbs conditions in a proper way, we numerically determine density profiles of nucleons, electrons, and condensed kaons. Importance of charge screening effects is elucidated and thereby we show that the Maxwell construction is effectively justified. Surface effect is also studied to figure out its effect on the density profiles.

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Exploring the QCD phase diagram with compact stars

Blaschke, D; Grigorian, H; Khalatyan, A; Voskresensky, DN

NUCLEAR PHYSICS B-PROCEEDINGS SUPPLEMENTS; vol. 141; pp. 137-142; year: 2005

Abstract: We investigate a nonlocal chiral quark model with separable 4-fermion interaction for the case of U(3) flavor symmetry, and show that strange quark matter is unlikely to occur in a large enough volume of a compact star to entail remarkable observational consequences. The phase diagram in the two-flavor sector of such model has a critical end point of the line of first order chiral/deconfinement phase transitions on which a triple point marks the junction with the critical line for second order phase transitions to two-flavor color superconductivity (2SC below T similar to 80 MeV. Stable hybrid star configurations with large quark matter core in a color superconducting phase can exist. A consistent cooling phenomenology requires that all quark species be gapped, the minimal pairing gap of the order of 10 - 100 keV.

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The above-threshold ionization spectrum in a strong linearly polarized laser field

Goreslavskii, SP; Popruzhenko, SV; Shvetsov-Shilovskii, NI; Shcherbachev, OV

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 100; pp. 22-30; year: 2005

Abstract: We use the saddle-point method to derive analytical expressions for the spectral-angular probability distributions of the ionization by a strong linearly polarized laser field in Keldysh's model that are valid for an arbitrary electron energy and adiabaticity parameter. We obtain asymptotic expansions of the general formulas in the multiphoton and tunneling regimes, analyze their accuracy, and formulate the validity conditions. We provide literal estimates of the parameters that characterize the properties and evolution of the distributions. (C) 2005 Pleiades Publishing, Inc.

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Lattice QCD constraints on hybrid and quark stars

Ivanov, YB; Khvorostukhin, AS; Kolomeitsev, EE; Skokov, VV; Toneev, VD; Voskresensky, DN

PHYSICAL REVIEW C; vol. 72; issue 2; year: 2005

Abstract: A QCD-motivated dynamical-quasiparticle model with parameters adjusted to reproduce the lattice-QCD equation of state is extrapolated from the region of high temperatures and moderate baryonic densities to the domain of high baryonic densities and zero temperature. The resulting equation of state matched with realistic hadronic equations of state predicts a phase transition into the quark phase at higher densities than those reachable in neutron star interiors. This excludes the possibility of the existence of hybrid (hadron-quark) stars. Pure quark stars are possible and have low masses, small radii, and very high central densities. Similar results are obtained for a simple bag model with massive quarks, fitted to reproduce the same lattice results. Self-bound quark matter is also excluded within these models. Uncertainties in the present extrapolation are discussed. Comparison with standard bag models is made.

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Relativistic generalization of the keldysh ionization theory

Karnakov, BM; Mur, VD; Popov, VS

LASER PHYSICS; vol. 15; issue 11; pp. 1556-1567; year: 2005

Abstract: A relativistic generalization is proposed for the quasi-classical theory of the multiphoton ionization of atoms and ions in the presence of a high-intensity electromagnetic wave. The elliptical polarization of laser radiation is considered. Using the method of imaginary time, we find the subbarrier trajectory satisfying the classical equations of motion along which the electron tunneling takes place. The exponential factor in the ionization probability is calculated for an arbitrary adiabaticity parameter gamma, energy of level E-0, and a radiation ellipticity rho. An asymptotically accurate formula for the ionization rate of the atomic s level that involves the Coulomb, spin, and adiabatic corrections and the preexponential factor is derived for the low-frequency (gamma << 1) laser radiation. It is demonstrated that, in the limit E-0 -> mc(2), the results obtained are transformed into the formulas of the nonrelativistic Keldysh ionization theory. Numerical estimates show that the relativistic corrections to the ionization probability are significant in the case of multicharged ions with Z (.) 40-60 at intensities of no less than 10(22)-10(23) W/cm(2).

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Relativistic mean-field models with effective hadron masses and coupling constants, and rho(-) condensation

Kolomeitsev, EE; Voskresensky, DN

NUCLEAR PHYSICS A; vol. 759; issue 3-4; pp. 373-413; year: 2005

Abstract: We study relativistic mean-field models with hadron masses and coupling constants depending self-consistently on a scalar meson field. We demonstrate that by the field redefinition some models can be equivalently transformed into each other. Thereby the large variety of scaling functions for masses and couplings can be reduced to a restricted set of functions with a constrained dependence on a scalar field. We show how by choosing properly the latter scaling functions one may stiffen or soften the equation of state at high densities and simultaneously increase the threshold density for the direct Urca process without any change of the description of nuclear matter close to the saturation density. The stiffening of the equation of state might be motivated by recent neutron star mass measurements, whereas the increase of the threshold density for the direct Urca process (n(crit)(DU)) is motivated by the analysis of neutron star cooling data. The high value n(crit)(DU) also follows from the variational calculations of the A18 + delta v + UIX* Urbana-Argonne model. We demonstrate that if a rho meson is included in a mean-field model as a non-Abelian gauge boson, then there is a possibility for a charged rho-meson condensation in dense nuclear matter. We show that such a novel phase can be realized in neutron star interiors already for sufficiently low densities, typically similar to 3-4n(0), where no is the nuclear saturation density. In the framework of the relativistic mean field model the new phase arises in a second-order phase transition. The appearance of a rho(-) condensate significantly alters the proton fraction in a neutron star but changes moderately the equation of state. The neutrino emissivity of the processes involving a rho(-) meson condensate is estimated. (c) 2005 Elsevier B.V. All rights reserved.

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Nuclear "pasta" structures and the charge screening effect

Maruyama, T; Tatsumi, T; Voskresensky, DN; Tanigawa, T; Chiba, S

PHYSICAL REVIEW C; vol. 72; issue 1; year: 2005

Abstract: Nonuniform structures of the nucleon matter at subnuclear densities are numerically studied by means of the density functional theory with relativistic mean fields coupled with the electric field. A particular role of the charge screening effects is demonstrated.

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Summation of divergent series and Zeldovich's regularization method

Mur, VD; Pozdnyakov, SG; Popruzhenko, SV; Popov, VS

PHYSICS OF ATOMIC NUCLEI; vol. 68; issue 4; pp. 677-685; Abstract: A method for summing divergent series, including perturbation-theory series, is considered. This method is an analog of Zeldovich's regularization method in the theory of quasistationary states. It is shown that the method in question is more powerful than the well-known Abel and Borel methods, but that it is compatible with them (that is, it leads to the same value for the sum of a series). The constraints on the parameter domain that arise upon the removal of the regularization of divergent integrals by this method are discussed. The dynamical Stark shifts and widths of loosely bound s states in the field of a circularly polarized electromagnetic wave are Calculated at various values of the Keldysh adiabaticity parameter and the inultiquantum parameter. &COyear:; 2005 Pleiades Publishing, Inc.

Abstract: A method for summing divergent series, including perturbation-theory series, is considered. This method is an analog of Zeldovich's regularization method in the theory of quasistationary states. It is shown that the method in question is more powerful than the well-known Abel and Borel methods, but that it is compatible with them (that is, it leads to the same value for the sum of a series). The constraints on the parameter domain that arise upon the removal of the regularization of divergent integrals by this method are discussed. The dynamical Stark shifts and widths of loosely bound s states in the field of a circularly polarized electromagnetic wave are Calculated at various values of the Keldysh adiabaticity parameter and the inultiquantum parameter. &COyear:; 2005 Pleiades Publishing, Inc.

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A relativistic electron in a focused laser pulse

Narozhny, NB

LASER PHYSICS; vol. 15; issue 10; pp. 1458-1476; year: 2005

Abstract: A realistic three-dimensional model for a focused high-intensity laser pulse in vacuum based on an exact solution of the Maxwell equations is described. Relativistic dynamics of an electron submitted to such a pulse is described by equations of motion with a ponderomotive potential. Symmetry of the ponderomotive potential is governed by a single parameter determined by the relative contribution of e- and h-polarized waves (waves with only either the electric or magnetic vector being transverse, respectively) to the laser pulse. It is shown that this parameter can be chosen to provide quantitative agreement of the developed theory with the experimental results of Malka et aL [Phys. Rev. Lett. 78, 3314 (1997)], who detected angular asymmetry in the spatial pattern of electrons accelerated in vacuum by a high-intensity laser pulse. The probability of electron-positron pair creation by a focused laser pulse is calculated. It is shown that pair production is possible only in an e-polarized electromagnetic wave. It is argued that there exists a natural physical limit for attainable focused laser pulse intensities. This limit is posed by the pulse energy loss due to the effect of pair creation.

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Sensitive behavior of 2 nu beta beta-decay amplitude within QRPA and broken SU(4) symmetry in nuclei

Rodin, VA; Urin, MH; Faessler, A

NUCLEAR PHYSICS A; vol. 747; issue 2-4; pp. 295-307; year: 2005

Abstract: Making use of an identity transformation independent of a nuclear model, we represent the 2vbetabeta-amplitude as a sum of two terms. One term accounts for most of the sensitivity of the original 2vbetabeta-amplitude to g'(pp) for realistic g'(pp) similar or equal to 1 (with g'(pp) being the ratio of the triplet and singlet p-p interaction strengths) and is determined by a specific energy-weighted sum rule. The sum rule depends only on the particle-particle residual interaction (being linear function of g'(pp) in the QRPA) and passes through zero at the point g'(pp) = 1 where the Wigner SU(4) symmetry is restored in the p-p sector of the Hamiltonian. The second term in the decomposition of the 2vbetabeta-amplitude is demonstrated within the QRPA to be a much smoother function for the realistic values of g'(pp) than the original 2vbetabeta-amplitude. This term is mainly determined by the intensity of the spin-orbit interaction of the nuclear mean field. Thus, the analysis of the present work reveals the reasons for the sensitivity of the 2vbetabeta-amplitude to different components of the nuclear Hamiltonian and thereby can help in constraining nuclear model uncertainties in calculations of the amplitude. (C) 2004 Elsevier B.V. All rights reserved.

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Structured mixed phase at charged kaon condensation

Maruyama, T; Tatsumi, T; Voskresensky, DN; Tanigawa, T; Chiba, S

NUCLEAR PHYSICS A; vol. 749; pp. 186C-189; year: 2005

Abstract: Non-uniform structures of the mixed phase at the first-order phase transition to the charged kaon condensation are studied using the density functional theory within the relativistic mean-field model. Including the electric field effects and applying Gibbs conditions in a proper way, we numerically determine density profiles of nucleons, electrons and condensed kaons. The importance of the charge screening effects is elucidated and thereby we show that the Maxwell construction is effectively justified.

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Magnetic impurity particle states on the short-range potential of arbitrary depth

Andreev, SP; Pavlova, TV

LASER PHYSICS; vol. 14; issue 2; pp. 174-178; year: 2004

Abstract: A model-independent problem of the Landau electron scattering in the band (0 less than or equal to N < L-2/r(c)(2)) with an arbitrary moment \m\ = l by a small-radius center (r(c) much less than L, where L = rootch/eH is the magnetic length) of arbitrary depth is solved. The wavefunctions ofthe bound magnetic impurity (MI) states are obtained. It is demonstrated that the poles of the derived scattering amplitude determines a spectrum of the bound and quasi-bound MI particle states at the center in different Landau bands. The behavior of the magnetic-impurity levels (real parts and widths) is investigated as a function of the potential depth of an individual impurity, the electron moment, and the Landau band number. The results of recent works (see [1, 2]) are specified. The general regularities of the kinetic coefficients (depending on the interaction of the charge carriers with neutral impurities of arbitrary depths) related to the features of the spectrum of the MI states are discussed.

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Unruh quantization in the presence of a condensate

Belinski, VA; Narozhny, NB; Fedotov, AM; Mur, VD

PHYSICS LETTERS A; vol. 331; issue 6; pp. 349-353; year: 2004

Abstract: We have shown that the Unruh quantization scheme can be realized in Minkowski spacetime in the presence of Bose-Einstein condensate containing infinite average number of particles in the zero boost mode and located basically inside the light cone. Unlike the case of an empty Minkowski spacetime the condensate provides the boundary conditions necessary for the Fulling quantization of the part of the field restricted only to the Rindler wedge of Minkowski spacetime. (C) 2004 Elsevier B.V. All rights reserved.

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The equation of two-dimensional island growth on the incommensurable monocrystalline substrate

Devyatko, YN; Rogozhkin, SV; Fadeev, AV

MICRO- AND NANOELECTRONICS 2003; vol. 5401; pp. 450-456; year: 2004

Abstract: The growth of an isolated island on the monocrystal surface with the structure incommensurable to that of the island is considered in the framework of the Zel'dovich-Volmer theory. The equation for the growth of a round island in the periodical field of the surface is obtained. The growth rate is proved to be oscillating in time, and the possibility for the growth to stop is shown.

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Sublimation of cobalt in the neighborhood of the Curie point

Devyatko, YN; Rogozhkin, SV

HIGH TEMPERATURE; vol. 42; issue 4; pp. 581-586; year: 2004

Abstract: The results of experiments in sublimation of cobalt in the neighborhood of the Curie point are analyzed. The kinetics of sublimation are described under conditions of permanent evacuation of the gas phase of cobalt. A magnetic model is suggested, which makes it possible to derive a quantitatively correct correlation between the Curie point and exchange splitting for Ni and Co. The contribution of magnetic interactions to the energy of sublimation of monatomic magnetic is calculated.

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Coulomb asymmetry in above-threshold ionization

Goreslavski, SP; Paulus, GG; Popruzhenko, SV; Shvetsov-Shilovski, NI

PHYSICAL REVIEW LETTERS; vol. 93; issue 23; year: 2004

Abstract: A new method for including effects of the Coulomb potential in strong-field laser atom interaction is presented. The model is tested by comparing its results with experimental data of energy resolved angular distributions of photoelectrons. For elliptical polarization these exhibit a strong asymmetry. Our theory shows that this strong asymmetry for the low-energy electrons is induced by a small Coulomb force acting on the tunneling electron just after the exit of the tunnel. This is in contrast to the situation for high electron energies where the asymmetry arises via rescattering by the parent ion.

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Dispersion and attenuation of surface shear acoustic waves with horizontal polarization on the free statistically rough surface of the hexagonal crystal

Kosachev, VV; Gandurin, YN; Barsukov, KV

PHYSICS OF THE LID STATE; vol. 46; issue 10; pp. 1954-1960; year: 2004

Abstract: Expressions for dispersion of the phase velocity and inverse damping depth of surface acoustic waves with shear horizontal polarization are derived in an analytical form within perturbation theory using the modified mean-field method for the Z-cut hexagonal crystal with a free statically rough surface. Both two- and one-dimensionally rough surfaces are considered. The one-dimensionally rough surface is considered as a special case of the two-dimensionally rough surface. It is shown that shear surface waves with horizontal polarization cannot exist on the flat surface of the Z-cut hexagonal crystal. The derived expressions are studied analytically and numerically in the entire frequency range accessible in perturbation theory. The long-wavelength limit (most interesting from the experimental point of view) is considered, where the wavelength is much longer than the roughness correlation radius. The conditions for the existence of SH-polarized waves are determined for both roughness types. It is shown that dispersion and attenuation of SH polarized waves are qualitatively similar in character to those we considered previously for an isotropic medium. (C) 2004 MAIK "Nauka / Interperiodica".

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Structured mixed phase in kaon condensation

Maruyama, T; Tatsumi, T; Voskresensky, DN; Tanigawa, T; Chiba, S; Maruyama, T

PROGRESS OF THEORE CAL PHYSICS SUPPLEMENT; issue 156; pp. 145-146; year: 2004

Abstract: We study non-uniform structures of the mixed phase during the first-order kaon condensation, using the density functional theory with the relativistic mean-field model. Including the Coulomb potential and applying the Gibbs conditions in a proper way, we numerically determine the density profiles of nucleons, electrons and condensed kaons. The importance of the Coulomb screening effects is elucidated and thereby we suggest that the Maxwell construction is effectively justified.

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On e(+)e(-) pair production by colliding electromagnetic pulses

Narozhny, NB; Bulanov, SS; Mur, VD; Popov, VS

JETP LETTERS; vol. 80; issue 6; pp. 382-385; year: 2004

Abstract: Electron-positron pair production from vacuum in an electromagnetic field created by two counterpropagating focused laser pulses interacting with each other is analyzed. The dependence of the number of produced pairs on the intensity of a laser pulse and the focusing parameter is studied with a realistic three-dimensional model of the electromagnetic field of the focused wave, which is an exact solution of the Maxwell equations. It has been shown that e(+)e(-) pair production can be experimentally observed when the intensity of each beam is I similar to 10(26) W/cm(2), which is two orders of magnitude lower than that for a single pulse. (C) 2004 MAIK "Nauka/Interperiodica".

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Reply to "Comment on 'Boundary conditions in the Unruh problem'"

Narozhny, NB; Fedotov, AM; Karnakov, BM; Mur, VD; Belinskii, VA

PHYSICAL REVIEW D; vol. 70; issue 4; year: 2004

Abstract: We reply to the preceding Comment by Fulling and Unruh criticizing our conclusion that principles of quantum field theory as of now do not give convincing arguments in favor of a universal thermal response of detectors uniformly accelerated in Minkowski space [Phys. Rev. D 65, 025004 (2002)]. We maintain our conclusion and present additional arguments to confirm it.

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On the relativistic theory of tunneling

Popov, VS; Karnakov, BM; Mur, VD

JETP LETTERS; vol. 79; issue 6; pp. 262-267; year: 2004

Abstract: A relativistic generalization of the semiclassical theory of tunneling and multiphoton ionization of atoms and ions in the field of a high-intensity electromagnetic wave with linear, circular, and elliptic polarization is constructed. The exponential factor in the ionization probability is calculated for arbitrary values of adiabaticity parameter gamma. In the case of low-frequency laser radiation, an asymptotically exact formula is derived for the ionization rate of the s atomic level, including the Coulomb, spin, and adiabatic corrections and the preexponential factor. (C) 2004 MAIK "Nauka / Interperiodica".

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Calculation of the anisotropic component of light in a dissipative medium with a linear scattering phase function

Remizovich, VS; Zhilkin, DV

LASER PHYSICS; vol. 14; issue 7; pp. 960-986; year: 2004

Abstract: The study of the propagation of photons systematically moving to the depth of a random dissipative medium is continued. Such photons reach a predetermined depth without changing the sign of the momentum projection p(z) along the internal normal to the surface of the substance. These photons form a so-called anisotropic component of the radiation intensity. It is demonstrated that the sign change of the momentum projection p(z) owing to the photon transition from the lower hemisphere to the upper one (the probability of this event differs from zero) is equivalent to introducing additional absorption in the equation for the anisotropic component of radiation. The effective absorption strongly affects virtually all characteristic parameters of the spatial-angular distribution of photons. An analytical expression for the intensity of the anisotropic component of the diffuse scattered radiation is obtained for the case when the law of single scattering is linear in terms of the scattering angle. Such a scenario can be realized in media with small-scale (in comparison with the wavelength) scattering centers. The effect of the mean cosine of the single-scattering angle on the zero and first azimuthal harmonics of the radiation intensity is analyzed. The behavior of the harmonics is studied at small and large depths. The most probable propagation angles of photons are calculated for various depths. The rotation of the body of brightness is demonstrated for the anisotropic component of the light intensity. The depth decay coefficient is determined. A simple analytical expression for the mean cosine of the anisotropic component of radiation and the probability of photon transition from the lower hemisphere to the upper one in the depth mode is derived. The results obtained for the anisotropic component of radiation are compared to similar results obtained for the total intensity.

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Hadron liquid with a small baryon chemical potential at finite temperature

Voskresensky, DN

NUCLEAR PHYSICS A; vol. 744; pp. 378-444; year: 2004

Abstract: We discuss general properties of a system of heavy fermions (including antiparticles) interacting with rather light bosons. First, we consider one diagram of Phi. The fermion chemical potential is assumed to be small, mu(f) less than or similar to T. Already for the low temperature, T much less than min(T-bl.f, m(b)), the fermion mass shell proves to be partially blurred due to multiple fermion rescatterings on virtual bosons, m(b) is the boson mass, T-bl.f (much less than m(f)) is the typical temperature corresponding to a complete blurring of the gap between fermion-antifermion continua, mf is the fermion mass. As the result, the ratio of the number of fermion-antifermion pairs to the number provided by the ordinary Boltzmann distribution becomes larger than unity (R-N > 1). For T greater than or similar to m(b)(*)(T) (hot hadron liquid, blurred boson continuum), m(b)(*)(T) is the effective boson mass, the abundance of all particles dramatically increases. Bosons behave as quasi-static impurities, on which heavy fermions undergo multiple rescatterings. The soft thermal loop approximation solves the problem. The effective fermion mass m(f)(*)(T) decreases with the temperature increase. For T greater than or similar to T-bl.f fermions are essentially relativistic particles. Due to the interaction of the boson with fermion-antifermion pairs, m(b)(*)(T) decreases leading to the possibility of the "hot Bose condensation" for T > T-cb. The phase transition might be of the second order or of the first order depending on the species under consideration. We study in detail properties of the system of spin 1/2 heavy fermions interacting with substantially lighter scalar neutral bosons (e.g., Nsigma system). Correlation effects of higher order diagrams of Phi are evaluated resulting in a suppression of vertices for T greater than or similar to m(b)(*)(T). The abundance of high-lying baryon resonances proves to be of the same order, as the nucleon-antinucleon abundance, or might be even higher for some species. Further we discuss the system of heavy fermions interacting with more light vector bosons (e.g., Nomega and Nrho) and then, with pseudo-scalar bosons (e.g., Npi). For the fermion-vector boson system correlation effects are incorporated by keeping the Ward identity. In case of the fermion-pseudoscalar boson system correlation effects are rather small. Finally, we allow for all interactions. We estimate R-N similar to 1.5 for T similar to m(pi)/2; T-bl.f proves to be near T-cb; both values are in the vicinity of the pton mass m(pi). (C) 2004 Elsevier B.V. All rights reserved.

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Fluctuations of the color-superconducting gap in hot and dense quark matter

Voskresensky, DN

PHYSICAL REVIEW C; vol. 69; issue 6; year: 2004

Abstract: Fluctuations of the color superconducting gap in hot and dense quark matter are investigated in terms of the phenomenological Ginzburg-Landau approach. Our estimates show that fluctuations of the di-quark gap may strongly affect some of thermodynamic quantities even far below and above the critical temperature. If the critical temperature of the di-quark phase transition were rather high one could expect a manifestation of fluctuations of the di-quark gap in the course of heavy ion collisions.

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Overtones of isoscalar giant resonances in medium-heavy and heavy nuclei

Gorelik, ML; Safonov, IV; Urin, MH

PHYSICAL REVIEW C; vol. 69; year: 2004

Abstract: A semimicroscopic approach based on both the continuum random-phase-approximation method and a phenomenological treatment of the spreading effect is extended and applied to describe the main properties (particle-hole strength distribution, energy-dependent transition density, partial direct-nucleon-decay branching ratios) of the isoscalar giant dipole, second monopole, and second quadrupole resonances. The abilities of the approach are checked by description of the gross properties of the main-tone resonances. Calculation results obtained for the resonances in a few singly- and doubly-closed-shell nuclei are compared with available experimental data.

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e(+)e(-)-pair production by a focused laser pulse in vacuum

Narozhny, NB; Bulanov, SS; Mur, VD; Popov, VS

PHYSICS LETTERS A; vol. 330; issue 1-2; pp. 1-6; year: 2004

Abstract: The probability of electron-positron pair creation by a focused laser pulse is calculated. For description of the focused laser pulse we use a 3-dimensional model of the electromagnetic field which is based on an exact solution of Maxwell equations. There exists two types of focused waves: e- and h-polarized waves with only either electric, or magnetic vector being transverse respectively. It is shown that pair production is possible only in e-polarized electromagnetic wave. The dependence of the pair production probability on the intensity of the laser pulse is obtained. It is argued that there exists a natural physical limit for attainable focused laser pulse intensities. This limit is posed by the pulse energy loss due to the effect of pair creation. (C) 2004 Elsevier B.V. All rights reserved.

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Landau damping in thin films irradiated by a strong laser field

Zaretsky, DF; Korneev, PA; Popruzhenko, SV; Becker, W

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OP CAL PHYSICS; vol. 37; issue 24; pp. 4817-4830; year: 2004

Abstract: The rate of linear collisionless damping (Landau damping) in a classical electron gas confined to a heated ionized thin film is calculated. The general expression for the imaginary part of the dielectric tensor in terms of the parameters of the single-particle self-consistent electron potential is obtained. For the case of a deep rectangular well, it is explicitly calculated as a function of the electron. temperature in the two limiting cases of specular and diffuse reflection of the electrons from the boundary of the self-consistent potential. For realistic experimental parameters, the contribution of Landau damping to the heating of the electron subsystem is estimated. It is shown that for films with a thickness below about 100 nm and for moderate laser intensities it may be comparable with or even dominate over electron-ion collisions and inner ionization.

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Quantum cyclotron resonance due to neutral impurities of arbitrary depth

Andreev, SP; Pavlova, TV

LASER PHYSICS; vol. 13; issue 6; pp. 897-901; year: 2003

Abstract: A formula describing the absorption line of quantum cyclotron resonance (QCR) in semiconductors corresponding to the scattering of charge carriers by neutral impurities of small radius r(c) (r(c) much less than l, l is the magnetic length) is derived. This formula is applicable within a broad range of magnetic fields, temperatures (0 less than or equal to T much less than homega(H), omega(H) is the cyclotron frequency), and frequency detunings (Deltaomega equivalent to omega - omega(H) much less than omega(H), omega is the frequency of the electric field). In contrast to the earlier works (see [1, 2] and references therein), we neither impose limitations on the depth of the potential of the scattering center nor assume that the mixing of Landau levels due to a single center is weak. A quantum kinetic integrodifferential equation for the one-electron density matrix averaged over the arrangement of scatterers is derived and solved in the linear approximation in the concentration of impurities. Calculations based on the gradient-invariant approach developed in [3] are performed only with the use of QCR conditions (homega(H) much greater than T, Deltaomega much less than omega(H)). Importantly, we were able to calculate the collision integral due to the use of exact wave functions of the problem of electron scattering from a short-range potential in a uniform magnetic field [4]. Comparison of the calculated half-width of the QCR absorption line deltaomega(T, H) with experimental results (obtained with infrared lasers, Figs. 1-3) indicates that the agreement between theoretical predictions and experimental data is much better than in all the earlier theoretical studies.

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Nonlinear Mie resonance excitation in clusters irradiated by a strong IR laser field

Fomichev, SV; Popruzhenko, SV; Zaretsky, DF

LASER PHYSICS; vol. 13; issue 9; pp. 1188-1195; year: 2003

Abstract: A collective electron dynamics of a large cluster irradiated by strong linearly polarized IR laser pulses is considered. The nonlinear equation of center-of-mass motion of an electron cloud driven by a laser field is investigated for the particular case of a neutral cluster. The analysis of this equation demonstrates an appreciable presence of the third harmonic of the fundamental frequency in the internal electric field inside a cluster. It is shown that, for clusters with radii R = 100 Angstrom irradiated by a field with a peak intensity of I = 10(16) W/cm(2), the electric field strength of tripled fundamental frequency can be of the same order as the fundamental field strength. This result is applied for the interpretation of recent experimental data. In particular, the yield enhancement of both highly charged ions and X rays from clusters irradiated by a strong laser field, with respect to simple atomic species, is discussed. The cross section of third harmonic generation versus both the cluster and laser field parameters is analyzed.

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Laser-induced nonlinear excitation of collective electron motion in a cluster

Fomichev, SV; Popruzhenko, SV; Zaretsky, DF; Becker, W

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OP CAL PHYSICS; vol. 36; issue 18; pp. 3817-3834; year: 2003

Abstract: We consider the nonlinear collective electron dynamics inside a large cluster irradiated by a strong linearly polarized short (less than or equal to0.1 ps) laser pulse. The equation of the centre-of-mass motion of the electron cloud driven by the strong laser field is derived using the approximation of an incompressible medium. The analysis of this equation demonstrates the presence of odd harmonics of the fundamental frequency in the cluster dipole moment, and in both the internal and the scattered electric field. Both neutral and ionized clusters are considered. For clusters with radii R similar or equal to 100 Angstrom irradiated by a femtosecond titanium-sapphire laser with a peak intensity of I similar or equal to 10(16) W cm(-2), the internal electric field strength near the tripled fundamental frequency is shown to be of the same order as the field of the fundamental. The reason is that both for metallic and for laser-ionized van der Waals clusters the Mie surface-plasmon energy homega(M) is around 5 eV, which is close to three times the energy of a titanium-sapphire laser-field quantum. On the other hand, the condition for first-order resonance with the Mie frequency is not met during the presence of the main laser pulse, but only temporarily, either at the first onset of inner ionization on the leading edge of the pulse (for van der Waals clusters) or during the subsequent Coulomb explosion. In both cases, the ion density is reduced. The presence of a strong third harmonic leads, in particular, to the enhanced production of multiply charged ions in clusters irradiated by a strong laser field, as compared with isolated atoms. This point is discussed in the light of recent experimental results on the production of multiply charged ions in laser-cluster experiments. Third-harmonic generation by a cluster in a strong laser field, as a function of both the cluster and the laser-field parameters, is also considered.

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Semimicroscopic description of basic properties of isoscalar monopole and dipole excitations in medium-mass spherical nuclei

Gorelik, ML; Urin, MH

PHYSICS OF ATOMIC NUCLEI; vol. 66; issue 10; pp. 1883-1896; year: 2003

Abstract: A description of basic properties (strength function, transition density, probabilities of direct nucleonic decays) of isoscalar giant monopole (including an overtone) and dipole resonances in medium-mass spherical nuclei is proposed within a semimicroscopic approach. The approach relies on employing the random-phase approximation and involves taking exactly into account a single-particle continuum and some conditions of partial self-consistency and phenomenologically describing the Coupling of states of the particle-hole type to multiquasiparticle configurations. The results of the calculations that were performed for Zr-90, Sn-116,Sn-124, Sm-144, and Pb-208 nuclei are compared with available experimental data. (C) 2003 MAIK "Nauka/Interperiodica".

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Self-consistent approach to off-shell transport

Ivanov, YB; Knoll, J; Voskresensky, DN

PHYSICS OF ATOMIC NUCLEI; vol. 66; issue 10; pp. 1902-1920; year: 2003

Abstract: The properties of two forms of the gradient expanded Kadanoff-Baym equations, i.e., the Kadanoff-Baym and Botermans-Malfliet forms, suitable for describing the tran sport dynamics of particles and resonances with broad spectral widths, are discussed in context of conservation laws, the definition of a kinetic entropy, and the possibility of numerical realization. Recent results on exact conservations of charge and energy-momentum within Kadanoff-Baym form of quantum kinetics based on local coupling schemes are extended to two cases relevant in many applications. These concern the interaction via a finite-range potential and, relevant in nuclear and hadron physics, e.g., for the pion-nucleon interaction, the case of derivative coupling. (C) 2003 MAIK "Nauka/Interperiodica".

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The spectrum of a hydrogen atom in a superstrong magnetic field and the Zeldovich effect in the short-range Coulomb problem

Karnakov, BM

JETP LETTERS; vol. 77; issue 2; pp. 68-73; year: 2003

Abstract: We derive formulas that describe the energy spectrum of a hydrogen atom in a superstrong magnetic field for states with various magnetic quantum numbers. Comparison with available numerical calculations of the spectrum indicates that the results obtained are highly accurate. These results can be interpreted as a manifestation of the Zeldovich effect regarding the rearrangement of the hydrogen atomic spectrum under the influence of strong Coulomb potential distortion at short distances in the problem under consideration. (C) 2003 MAIK "Nauka/Interperiodica".

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A hydrogen atom in a superstrong magnetic field and the Zeldovich effect

Karnakov, BM; Popov, VS

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 97; issue 5; pp. 890-914; year: 2003

Abstract: We consider the problem of a hydrogen atom in a superstrong magnetic field, B > B-a = 2.35 x 10(9) G. The analytical formulas that describe the energy spectrum of this atom are derived for states with various quantum numbers n(rho) and m. A comparison with available calculations shows their high accuracy for B > B-a . We note that the derived formulas point to a manifestation of the Zeldovich effect, i.e., a rearrangement of the atomic spectrum under the influence of strong short-range Coulomb potential distortion. We discuss the relativistic corrections to level energies, which increase in importance with magnetic field and become significant for B greater than or similar to 10(14) G. We suggest the parameters in terms of which the Zeldovich effect has the simplest form. Analysis of our precision numerical calculations of the energy spectrum for a hydrogen atom in a constant magnetic field indicates that the Zeldovich effect is observed in the spectrum of atomic levels for superstrong fields, B greater than or similar to 5 x 10(11) G. Magnetic fields of such strength exist in neutron stars and, possibly, in magnetic white dwarfs. We set lower limits for the fields B-min required for the manifestation of this effect. We discuss some of the properties of atomic states in a superstrong magnetic field, including their mean radii and quadrupole moments. We calculated the probabilities of electric dipole transitions between odd atomic levels and a deep ground level. (C) 2003 MAIK "Nauka / Interperiodica".

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Rayleigh wave dispersion and attenuation on a statistically rough free surface of a hexagonal crystal

Kosachev, VV; Gandurin, YN

PHYSICS OF THE LID STATE; vol. 45; issue 2; pp. 391-399; year: 2003

Abstract: Dispersion and attenuation of Rayleigh surface acoustic waves on a statistically rough free surface of a Z-cut hexagonal crystal were analytically studied using a modified mean-field method within the perturbation theory. Numerical calculations were carried out in the frequency range accessible for the perturbation theory using expressions for the real and imaginary parts of the complex frequency shift of Rayleigh waves caused by a slight surface roughness. The Rayleigh wave dispersion and attenuation in the Z-cut hexagonal crystal were shown to coincide qualitatively with those in an isotropic medium, differing only quantitatively. In the long-wavelength limit lambda > a, where a is the lateral roughness correlation length, explicit analytical expressions for the relative change in the phase velocity and the inverse damping depth of Rayleigh waves were derived and used in numerical calculations. (C) 2003 MAIK "Nauka / Interperiodica".

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Dispersion and attenuation of rayleigh waves at a one-dimensional random roughness of the free surface of a hexagonal crystal

Kosachev, VV; Gandurin, YN

PHYSICS OF THE LID STATE; vol. 45; issue 9; pp. 1808-1813; year: 2003

Abstract: Analytical expressions are derived for dispersion and attenuation of Rayleigh waves propagating along the statistically rough free surface of a hexagonal crystal (Z cut). The roughness under consideration is one-dimensional (the profile function of the roughness depends on one coordinate) and has the form of hollows of a random lattice. The results obtained earlier in the solution of an analogous problem for a two-dimensional roughness are used in the one-dimensional case. The relationships derived for the dispersion and attenuation of Rayleigh waves are treated analytically and numerically over the entire range of frequencies acceptable in the framework of the perturbation theory. It is shown that the dispersion and attenuation of Rayleigh waves are qualitatively similar to those observed in an isotropic medium. (C) 2003 MAIK "Nauka / Interperiodica".

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dt, d(3)He, and p alpha scattering in the vicinity of the He-5* and Li-5* resonances

Kulik, AV; Mur, VD

PHYSICS OF ATOMIC NUCLEI; vol. 66; issue 1; pp. 87-98; year: 2003

Abstract: It is shown that the simplest strong-interaction models (those that employ the Breit boundary condition and a delta-function potential) involving only three free parameters describe adequately the properties of the dt and d(3)He systems in the vicinity of the He-5*(3/2(+)) and Li-5*(3/2(+)) resonances-that is, at energies in the regions E less than or similar to 3Ec and E less than or similar to 2EC, where E-C is the corresponding Coulomb energy. For these systems, the complex values of the scattering length, of the effective range, and of the shape parameter are extracted from experimental data on the reaction cross section and proton polarization in palpha scattering (in the case of the d3He system). The astrophysical function is extrapolated to the low-energy region (0 less than or equal to E < 0.1E(C)), which is of importance for thermonuclear investigations, but which is hardly accessible to direct measurements. (C) 2003 MAIK "Nauka/lnterperiodica".

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Interaction between the field modes in the dynamical Casimir effect

Lozovik, YE; Narozhny, NB; Fedotov, AM; Berkov, A; Narozhny, N; Okun, L

I. Ya Pomeranchuk and Physics at the Turn of the Century; pp. 446-453; year: 2003

Abstract: Generation of photons in a nonstationary cavity is considered within the framework of one dimensional scalar model. The frequency distribution and the total number of created photons are estimated in the instantaneous approximation. It is shown that strong interaction between the cavity modes has essential influence on the process of photon creation.

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1/Q expansion for the energy spectrum of quantum dots

Lozovik, YE; Mur, VD; Narozhnyi, NB

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 96; issue 5; pp. 932-939; year: 2003

Abstract: A new method is proposed for calculating the energy spectrum and the wave functions of N - electron quantum dots with an arbitrary confining potential. The method consists in expansion with respect to a dimensionless quantum parameter 1/ Q, which is expressed in terms of the ratio of the characteristic Coulomb energy of electron - electron interaction to the characteristic energy of one- particle transition in a confining potential. Two- electron quantum dots with a parabolic confining potential in an external magnetic field are considered. Strongly correlated states of the system and the spin rearrangement in a strong magnetic field are analyzed. Analytic expressions are obtained for the energy and the wave functions of the system. It is shown that restriction of the analysis only to the first three terms in the quantum- parameter expansion gives an accuracy of one percent when calculating the energy even for values of Q on the order of unity, i. e., for the presently implementable GaAs quantum dots. The expressions for energy obtained are in a good agreement with the experimental data for quantum dots in a perpendicular magnetic field. (C) 2003 MAIK " Nauka/ Interperiodica".

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On the problem of negative ions photodetachment in intense circularly polarized laser field

Mur, VD; Popruzhenko, SV; Pozdnyakov, SG; Popov, VS

PHYSICS LETTERS A; vol. 316; issue 3-4; pp. 226-232; year: 2003

Abstract: We present the theoretical calculation of photodetachment rate of loosely bound atomic states in an intense circularly polarized monochromatic laser field. Different calculation methods are used: the perturbation theory with respect to laser field intensity, the semiclassical approximation and the exact numerical solution of transcendental equation for complex quasienergy of an atomic level. In the last case we use the regularization method for divergent integrals with Gamow wave function proposed by Zel'dovich. We present the comparison of semiclassical and exact results and discuss the accuracy of semiclassical approximation in the theory of ionization. Results are applied for the calculation of photodetachment rate for negative ions of hydrogen and alkali metals. (C) 2003 Published by Elsevier B.V.

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Zeldovich's regularization method in the theory of quasistationary states

Mur, VD; Pozdnyakov, SG; Popruzhenko, SV; Popov, VS

PHYSICS OF ATOMIC NUCLEI; vol. 66; issue 11; pp. 1964-1971; year: 2003

Abstract: The complex quasienergy, including the level width Gamma, is calculated for a loosely bound atomic state in an intense monochromatic laser field of circular polarization. The method proposed by Zeldovich for regularizing divergent integrals that involve the Gamow wave function is employed in this calculation. The convergence of the method is demonstrated, and the conditions of its applicability are indicated. (C) 2003 MAIK "Nauka/Interperiodica".

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Pair creation by homogenous electric field frim the point of view of an accelerated observer

Narozhny, NB; Mur, VD; Fedotov, AM

PHYSICS LETTERS A; vol. 315; issue 3-4; pp. 169-174; year: 2003

Abstract: With a special choice of gauge the operator of the Klein-Fock-Gordon equation in homogeneous electric field respects boost symmetry. Using this symmetry we obtain solutions for the scalar massive field equation in such a background (boost modes in the electric field). We calculate the spectrum of particles created by the electric field, as seen by an accelerated observer at spatial infinity of the right wedge of Minkowski spacetime. It is shown that the spectrum and the total number of created pairs measured by a remote uniformly accelerated observer in Minkowski spacetime are precisely the same as for inertial observers. (C) 2003 Elsevier B.V All rights reserved.

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Dynamical Casimir and Lamb effects and entangled photon states

Narozhny, NB; Fedotov, AM; Lozovik, YE

LASER PHYSICS; vol. 13; issue 2; pp. 298-304; year: 2003

Abstract: An atom interacting with a quantized electromagnetic field in a cavity with time-dependent parameters is considered. Variation of the cavity parameters results in nonstationary dynamics of the field which leads, in turn, to excitation of the atom, even if photons were initially absent in the cavity. We distinguish three mechanisms of such excitation: excitation due to absorption of real photons created by the dynamical Casimir effect, excitation due to absorption of virtual photons during the transient process, and excitation due to nonadiabatic parametric modulation of the atomic Lamb shift. The last mechanism is a new effect in cavity quantum electrodynamics (dynamical Lamb effect). The resulting quantum state of the system consisting of the atom and the created photons is an entangled state, i.e., a state containing Bell-Einstein-Podolsky-Rosen correlations. The entanglement properties of the states of the system, in principle, can be utilized for physical realization of quantum (rates for quantum computations. As we demonstrate, one can create entangled states that are arbitrarily close to the pure Bell-Einstein-Podolsky-Rosen states under certain conditions (high-Q cavity tuned in the final state to the atomic transition frequency).

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Particle creation by a constant homogeneous electric fields in the Rindler and Milne reference frames

Narozhny, NB; Fedotov, AM; Mur, VD; ED Berkov, A; Narozhny, N; Okun, L

I. Ya Pomeranchuk and Physics at the Turn of the Century; pp. 465-472; year: 2003

Abstract: With a special choice of gauge the operator of the Klein-Fock-Gordon equation in homogeneous electric field respects boost symmetry. Using this symmetry we obtain solutions for the scalar massive field equation in such a background (boost modes in the electric field). We calculate the spectrum of particles created by the electric field, as seen by an accelerated observer at spatial infinity of the right wedge of Minkowski space-time. It is shown that the spectrum and the total number of created pairs measured by a remote uniformly accelerated observer in Minkowski space-time are precisely the same as for inertial observers. This means in particular that the Unruh effect does not exist.

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Two aspects of the Unruh problem

Narozhny, NB; Fedotov, AM; Mur, VD; Belinski, VA

NUOVO CIMENTO DELLA CIETA ITALIANA DI FissueICA B-GENERAL PHYSICS RELA VITY ASTRONOMY AND MATHEMA CAL PHYSICS AND METHODS; vol. 118; issue 10-12; pp. 1125-1136; year: 2003

Abstract: We discuss field-theoretical and detector aspects of the Unruh problem. We show that the existing variants of the field-theoretical approach do not give compelling evidence for the universal behavior attributed to all uniformly accelerated detectors. We present an example of a uniformly accelerating detector which does not reveal the universal thermal response of the Unruh type.

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Asymmetric emission of rescattered photoelectrons in intense laser fields with elliptical polarization

Shvetsov-Shilovski, NI; Popruzhenko, SV; Goreslavski, SP

LASER PHYSICS; vol. 13; issue 8; pp. 1054-1063; year: 2003

Abstract: Angular distributions generated by an intense elliptically polarized laser field in the high energy part of the above-threshold ionization spectrum are presented and discussed in the context of recent experimental observations.

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Nonlinear waves in bismuth

Skobov, VG; Chernov, AS

PHYSICS OF THE LID STATE; vol. 45; issue 10; pp. 1860-1865; year: 2003

Abstract: The propagation of short radio waves in a bismuth crystal in a constant magnetic field H aligned parallel to the bisecting axis oriented normally to the surface of the crystal plate is investigated theoretically. In this geometry, spatial inhomogeneity of the wave field has a weak effect on electrons and a strong effect on holes. It is demonstrated that, in a certain range of magnetic field strengths H, the bismuth crystal is characterized by two modes, namely, a helicon and a doppleron, whose damping is governed by cyclotron absorption of holes. For small amplitudes of the wave field in a linear regime, the damping lengths of both modes are relatively short due to cyclotron absorption. In a nonlinear regime, the magnetic field of the radio wave captures holes responsible for cyclotron absorption. As a result, the absorption is suppressed and the damping lengths of the helicon and the doppleron increase drastically. The excitation of these modes in the bismuth plate results in the fact that the dependence of the impedance of the plate on the magnetic field strength H exhibits resonance behavior and the transmittance of the plate increases by more than two orders of magnitude. It is shown that this effect should manifest itself at frequencies of the order of a few megahertzes in relatively weak magnetic fields (of the order of a few tens of oersteds).

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Stability of subatomic carbon films on metal surfaces against low-energy gas ion bombardment

Suvorov, AL; Babaev, VP; Zaluzhnyi, AG; Devyatko, YN; Lazarev, NE; Zaluzhnyi, AA

TECHNICAL PHYSICS; vol. 48; issue 1; pp. 104-109; year: 2003

Abstract: The earlier developed original experimental technique for measuring and analyzing the parameters of low-frequency fluctuations of the field-emission current in metal film systems is used to measure the sputtering yield Y-f of carbon films (with a coverage Theta ranging from 1 to 4) applied on Fe, Nb, Ta, and U substrates. The value of Y-f is calculated by an expression derived within a theoretical model developed. The sputtering ratios were measured for the case when the carbon films are sputtered by H+ and He+ ions with an energy E-i between 2 and 10 keV. With Theta fixed, the energy dependences of Y-f are obtained for each of the ions. In addition, for each of the ions, the Theta dependences of Y-f are found for several values of E-i. In all the cases, the measured values of Y-f far exceed those for pure carbon. With another original technique that combines field-ion microscopy (FIM) and precise measurement of current and/or luminous properties of local regions in FIM images, the energy thresholds E-th of sputtering carbon films applied on the metal surfaces are found. The energy distributions of Y-f in the near-threshold energy range for various Theta are obtained.

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Charge screening at first order phase transitions and hadron-quark mixed phase

Voskresensky, DN; Yasuhira, M; Tatsumi, T

NUCLEAR PHYSICS A; vol. 723; issue 1-2; pp. 291-339; year: 2003

Abstract: The possibility of structured mixed phases at first order phase transitions in neutron stars is re-examined by taking into account charge screening and surface effects. The transition from the hadron npe phase to the quark phase is studied. Two possibilities, the mixed phase and two separate phases given by the double-tangent (Maxwell) construction are considered. Inhomogeneous profiles of the electric potential and their contribution to the energy are analytically calculated. The electric field configurations determine the droplet size and the geometry of structures. (C) 2003 Published by Elsevier Science B.V.

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Medium effects in the pion-pole mechanism [gamma gamma ->pi(0)->nu(R)(nu)over-bar(L)(nu(L)(nu)over-bar(R))] of neutron star cooling

Arretche, F; Natale, AA; Voskresensky, DN

PHYSICAL REVIEW C; vol. 68; issue 3; year: 2003

Abstract: Nuclear medium effects in the neutrino cooling of neutron stars through the reaction channel gammagamma-->pi(0)-->nu(R)nu$$($) over bar (L)(nu(L)(&nu;) over bar (R)) are incorporated. Throughout the paper we discuss different possibilities of right-handed neutrinos, massive left-handed neutrinos, and standard massless left-handed neutrinos (reaction is then allowed only with medium modified vertices). It is demonstrated that multiparticle effects suppress the rate of this reaction channel in the dense hadron matter by 6-7 orders of magnitude that does not allow to decrease existing experimental upper limit on the corresponding pi(0)nu(&nu;) over bar coupling. Other possibilities of the manifestation of the given reaction channel in different physical situations, e.g., in the quark color superconducting cores of the most massive neutron stars, are also discussed. We demonstrate that in the color-flavor-locked superconducting phase for temperatures Tless than or similar to0.1-10 MeV (depending on the effective pion mass and the decay width) the process is feasibly the most efficient neutrino cooling process, although the absolute value of the reaction rate is rather small.

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Negative kaons in dense baryonic matter

Kolomeitsev, EE; Voskresensky, DN

PHYSICAL REVIEW C; vol. 68; issue 1; year: 2003

Abstract: The kaon polarization operator in dense baryonic matter of arbitrary isotopic composition is calculated including s- and p-wave kaon-baryon interactions. The regular part of the polarization operator is extracted from the realistic kaon-nucleon interaction based on the chiral and 1/N-c expansion. Contributions of Lambda(1116), Sigma(1195), Sigma*(1385) resonances are taken explicitly into account in the pole and regular terms with the inclusion of mean-field potentials. The baryon-baryon correlations are incorporated and fluctuation contributions are estimated. Results are applied for K- in neutron star matter. Within our model a second-order phase transition to the s-wave K- condensate state occurs at rho(c)greater than or similar to4rho(0) with baryon-baryon correlations included. We show that a second-order phase transition to the p-wave K- condensate state may occur at densities rho(c)similar to(3-5)rho(0) dependent on the parameter choice. We demonstrate that a first-order phase transition to a proton-enriched (approximately isospin-symmetric) nucleon matter with a p-wave K- condensate can occur at smaller densities, rholess than or similar to2rho(0). The transition is accompanied by the suppression of hyperon concentrations.

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On the Fermi and Gamow-Teller strength distributions in medium-heavy mass nuclei*

Rodin, VA; Urin, MH

PHYSICS OF ATOMIC NUCLEI; vol. 66; issue 12; pp. 2128; year: 2003

Abstract: An isospin-self-consistent approach based on the continuum- random-phase approximation (CRPA) is applied to describe the Fermi and Gamow-Teller strength distributions within a wide excitation-energy interval. To take into account nucleon pairing in open-shell nuclei, we formulate in isospin-self-consistent version of the proton-neutron-quasiparticle (pn-QCRPA) approach by incorporating the BCS model into the CRPA method. The isospin and configurational splittings of the Gamow-Teller giant resonance are analyzed in single-open-shell nuclei. The calculation results obtained for the Bi-208, Nb-90, and Sb isotopes are compared with the available experimental data.

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Hadron-quark mixed phase in neutron stars

Tatsumi, T; Yasuhira, M; Voskresensky, DN

NUCLEAR PHYSICS A; vol. 718; pp. 359C; year: 2003

Abstract: Possibility of structured mixed phases at first order phase transitions is examined by taking into account of charge screening and surface effects. Hadron-quark phase transition in dense neutron star interiors is considered as a concrete example.

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Line broadening in quantum cyclotron resonance due to neutral impurities of arbitrary depth

Andreev, SP; Pavlova, TV

LASER PHYSICS; vol. 12; issue 11; pp. 1381-1385; year: 2002

Abstract: A theory of a quantum cyclotron resonance (QCR) in semiconductors, when charge carriers with an isotropic effective mass, scattered by neutral impurities of a small radius r(c) (r(c) < l, l = root(ch/eH is a magnetic length) and an arbitrary depth, is developed. The only limitation on the applicability of this theory (except the QCR conditions homega(H) much greater than T and omega - omega(H) much less than omega(H), where omega(H) is the cyclotron frequency, omega is the frequency of the electric field, and T is the temperature of a semiconductor) is the use of a linear approximation of the impurity concentration for the calculation of the collision integral.(1) Our approach substantially improves the agreement between theoretical predictions and experimental results as compared to all the previous studies (see [1, 2] and references therein).

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Theoretical aspects of sputtering of magnetic materials near the Curie point

Devyatko, YN; Rogozhkin, SV

VACUUM; vol. 66; issue 2; pp. 123-132; year: 2002

Abstract: A new approach for description of anomalies in Sputtering of magnetic materials near the Curie temperature has been proposed. The energy of sublimation is shown to have no anomalies in this temperature range. The anomalies in sputtering of magnetic materials are connected with significant increase of evaporation of weakly-bounded surface atoms from the hot spots created by incident ions. (C) 2002 Elsevier Science Ltd. All rights reserved.

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Kinetics of desorption from the surface of magnetic materials far from the Curie point

Devyatko, YN; Markun, PN

IZVESTIYA AKADEMII NK SERIYA FIZICHESKAYA; vol. 66; issue 4; pp. 527-532; year: 2002

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The reaction of decay of slow positronium during interaction with metal surface

Gusarov, IA; Korovushkin, AV; Osadchiev, VM

IZVESTIYA AKADEMII NK SERIYA FIZICHESKAYA; vol. 66; issue 7; pp. 1048-1053; year: 2002

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The energy spectrum of two-electron circular quantum dots in external electromagnetic fields

Lozovik, YE; Mur, VD; Narozhnyi, NB; Fofanov, MS

LASER PHYSICS; vol. 12; issue 4; pp. 764-768; year: 2002

Abstract: Two-dimensional two-electron quantum dots with a parabolic binding potential in an external magnetic field and the field of a circular monochromatic wave are considered. Analytical expression for the energies and wave functions are derived with the use of expansion in a dimensionless quantum. parameter 1/Q, related to the steepness of the binding potential. It is shown that already the first three terms in the 1/Q expansion provide a percent accuracy in energy calculations with Q similar to 1, i.e., for experimentally realizable GaAs-based quantum dots. An analytical expression for singlet-triplet crossing is derived. This expression agrees well with the relevant experimental value for quantum dots in a perpendicular magnetic field. The spectrum of quasienergies is studied for quantum dots in the field of a circular monochromatic wave.

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Anisotropy of angular distribution and energy spectrum of atoms in the linear cascade of collisions

Marinyuk, VV; Remizovich, VS

IZVESTIYA AKADEMII NK SERIYA FIZICHESKAYA; vol. 66; issue 4; pp. 457-461; year: 2002

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On the Zel'dovich regularization method in the theory of quasistationary states

Mur, VD; Pozdnyakov, SG; Popov, VS; Popruzhenko, SV

JETP LETTERS; vol. 75; issue 5; pp. 249-252; year: 2002

Abstract: Complex quasienergy and level width are calculated for a weakly bound atomic state in an intense circularly polarized monochromatic laser field using the method suggested by Zel'dovich for the regularization of divergent integrals with the Gamow wave function. It is demonstrated that this method converges, and the conditions for its applicability are indicated. These results are used to discuss the accuracy of the semiclassical approximation in the problems of ionization theory. (C) 2002 MAIK "Nauka / Interperiodica".

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Boundary conditions in the Unruh problem

Narozhny, NB; Fedotov, AM; Karnakov, BM; Mur, VD; Belinskii, VA

PHYSICAL REVIEW D; vol. 65; issue 2; Abstract: According to Unruh, a detector moving with constant proper acceleration in empty Minkowski spacetime reveals universal-not depending on the inner structure of the detector-thermal response. We have analyzed the Unruh problem using both conventional and algebraic approaches to quantum field theory. It is shown that the Unruh quantization procedure implies setting a boundary condition for the quantum field operator which changes the topological properties and symmetry group of the spacetime and leads to a field theory in two disconnected left and right Rindler spacetimes instead of Minkowski spacetime. Thus we conclude that, in spite of the work over the last 25 years, there still remain serious gaps in grounding of the Unruh effect, and as of now there is no compelling evidence for the universal behavior attributed to all uniformly accelerated detectors.

Abstract: According to Unruh, a detector moving with constant proper acceleration in empty Minkowski spacetime reveals universal-not depending on the inner structure of the detector-thermal response. We have analyzed the Unruh problem using both conventional and algebraic approaches to quantum field theory. It is shown that the Unruh quantization procedure implies setting a boundary condition for the quantum field operator which changes the topological properties and symmetry group of the spacetime and leads to a field theory in two disconnected left and right Rindler spacetimes instead of Minkowski spacetime. Thus we conclude that, in spite of the work over the last 25 years, there still remain serious gaps in grounding of the Unruh effect, and as of now there is no compelling evidence for the universal behavior attributed to all uniformly accelerated detectors.

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Laser-induced recollision phenomena: Interference resonances at channel closings

Popruzhenko, SV; Korneev, PA; Goreslavski, SP; Becker, W

PHYSICAL REVIEW LETTERS; vol. 89; issue 2; year: 2002

Abstract: An analytical theory of the resonancelike phenomena in high-order above-threshold ionization is presented that explains details of the experimental spectra and theoretical simulations. It traces the observed features to the constructive interference of "quantum orbits" with long travel times at laser intensities where the N-photon ionization channels close. Characteristic differences show up between even and odd N. The effects are generic to all laser-induced recollision phenomena. For nonsequential double ionization, their signature in the momentum distribution of the final electrons is identified.

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The anisotropic component of optical radiation in a dissipative medium

Remizovich, VS; Zhilkin, DV

LASER PHYSICS; vol. 12; issue 3; pp. 541-557; year: 2002

Abstract: The main problem in the theory of transfer of stationary optical radiation in disordered media in the absence of any coherent and polarization effects in the regime of scattering when the photon frequency remains unchanged is to calculate the light intensity I(r, Omega). The quantity I(r, Omega) defines the mean flux of light energy at the point r along the unit vector of the photon velocity Omega = c/c. To determine the quantity I(r, Omega), one has to solve the relevant linearized kinetic equation-the transfer equation. In many situations, we deal with the propagation of broad radiation fluxes in uniform scattering media with plane boundaries, when the conditions of the so-called planar geometry are implemented. This important case will be considered below.

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Charge screening in hadron-quark mixed phase

Voskresensky, DN; Yasuhira, M; Tatsumi, T

PHYSICS LETTERS B; vol. 541; issue 1-2; pp. 93-100; year: 2002

Abstract: The possibility of structured mixed phases in first order phase transitions is examined. Charge screening and surface effects are considered for the hadron-quark phase transition indense neutron star interior.

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An example of a uniformly accelerated particle detector with non-Unruh response

Fedotov, AM; Narozhny, NB; Mur, V; Belinski, V

PHYSICS LETTERS A; vol. 305; issue 5; pp. 211-217; year: 2002

Abstract: We propose a scalar background in Minkowski spacetime imparting constant proper acceleration to a classical particle. In contrast to the case of a constant electric field the proposed scalar potential does not create particle-antiparticle pairs. Therefore, an elementary particle accelerated by such field is a more appropriate candidate for an "Unruh-detector" than a particle moving in a constant electric field. We show that the proposed detector does not reveal the universal thermal response of the Unruh type. (C) 2002 Elsevier Science B.V. All rights reserved.

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Delay-dependent amplification of a probe pulse via stimulated rayleigh scattering

Fedorov, MV; Popruzhenko, SV; Zaretsky, DF; Becker, W

PHYSICAL REVIEW LETTERS; vol. 88; issue 21; year: 2002

Abstract: Stimulated Rayleigh scattering of pump and probe light pulses of close carrier frequencies is considered. A nonzero time delay between the two pulses is shown to give rise to amplification of the delayed (probe) pulse accompanied by attenuation of the pump, both on resonance and off resonance. In either case, phase-matching effects are shown to provide a sufficiently large gain, which can exceed significantly direct one-photon absorption losses.

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Anisotropy of electrons accelerated by a high-intensity laser pulse

Narozhny, NB; Fofanov, MS

PHYSICS LETTERS A; vol. 295; issue 2-3; pp. 87-91; year: 2002

Abstract: We describe a realistic model for a focused high-intensity laser pulse in three dimensions. Relativistic dynamics of an electron submitted to such pulse is described by equations of motion with ponderomotive potential depending on a single free parameter in the problem, which we refer to as the "asymmetry parameter". It is shown that the asymmetry parameter can be chosen to provide quantitative agreement of the developed theory with experimental results of Malka et al. (Phys. Rev. Lett. 78 (1997) 3314) who detected angular asymmetry in the spatial pattern of electrons accelerated in vacuum by a high-intensity laser pulse. (C) 2002 Elsevier Science B.V. All rights reserved.

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Semimicroscopical description of the simplest photonuclear reactions accompanied by excitation of the giant dipole resonance in medium-heavy mass nuclei

Rodin, VA; Urin, MH

PHYSICAL REVIEW C; vol. 66; issue 6; year: 2002

Abstract: A semimicroscopical approach is applied to describe photoabsorption and partial photonucleon reactions accompanied by the excitation of the giant dipole resonance (GDR). The approach is based on the continuum random phase approximation (CRPA) with a phenomenological description for the spreading effect. The phenomenological isoscalar part of the nuclear mean field, momentum-independent Landau-Migdal particle-hole interaction, and separable momentum-dependent forces are used as input quantities for the CRPA calculations. The experimental photoabsorption and partial (n,gamma)-reaction cross sections in the vicinity of the GDR are satisfactorily described for Y-89, Ce-140, and Pb-208 target nuclei. The total direct-neutron-decay branching ratio for the GDR in Ca-48 and Pb-208 is also evaluated.

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Meissner effect for color superconducting quark matter

Sedrakian, DM; Blaschke, D; Shahabasyan, KM; Voskresensky, DN

PHYSICS OF PAR CLES AND NUCLEI; vol. 33; pp. S100-105; year: 2002

Abstract: The behavior of the magnetic field inside the superconducting quark matter core of a neutron star is investigated in the framework of the Ginzburg-Landau theory. We take into account the simultaneous coupling of the diquark condensate field to the usual magnetic and to the glomagnetic gauge fields. We solve the problem for three different physical situations: a semi-infinite region with a planar boundary, a spherical region, and a cylindrical region. We show that Meissner currents near the quark core boundary effectively screen the external static magnetic field.

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On description of photonuclear reactions accompanied by excitation of the giant dipole resonance

Rodin, VA; Urin, MH; Fujiwara, M; Shima, T

PROCEEDINGS OF THE INTERNA ONAL SYMPOSIUM ON ELECTROMAGNE C INTERAC ONS IN NUCLEAR AND HADRON PHYSICS; pp. 477-486; year: 2002

Abstract: A semimicroscopical approach is applied to describe the photoabsorption and partial photonucleon reactions accompanied by excitation of the giant dipole resonance (GDR). The approach is based on both continuum-RPA (CRPA) and a phenomenological description for doorway-state coupling to many-quasi particle configurations. Apart from a phenomenological mean field, the separable isovector momentum-dependent forces and momentum-independent Landau-Migdal particle-hole interaction are used as the input quantities for CRPA calculations. The photoabsorption and partial (n, gamma)-reaction cross sections in the vicinity of the GDR are satisfactorily described for Y-89, Ce-140 and Pb-208 target nuclei.

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Magnetic-impurity conductivity oscillations in semiconductors with a sharply anisotropic effective mass of charge carriers

Andreev, SP; Pavlova, TV

LASER PHYSICS; vol. 11; issue 12; pp. 1357-1364; year: 2001

Abstract: We develop a self-consistent theory of magnetic-impurity oscillations of static conductivity in semiconductors with spheroidal isoenergy surfaces of charge carriers scattered by small-scale neutral donors. The influence of the anisotropy of effective mass on the electron wave function of the impurity is taken into consideration. This effect makes the potential of an individual impurity center aspherical. It is shown that both the longitudinal and transverse conductivities display oscillations periodic in the magnetic field with H-1/4 due to the long-range character of the potential of an individual center, which is due to the absence of the spherical symmetry in the case when the magnetic field is oriented in the direction corresponding to a heavy mass, H parallel to m(parallel to). It is demonstrated that these oscillations arise due to the fact that magnetic-impurity electron states in a neutral impurity form a continuum in the case when the magnetic field strength is decreased. The possibility of detecting such oscillations in IV-group semiconductors is discussed.

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Point defects at low-index surfaces of fcc metals: Formation energies of vacancies and adatom-vacancy pairs

Devyatko, YN; Rogozhkin, SV; Fadeev, AV

PHYSICAL REVIEW B; vol. 63; issue 19; pp. art. no.-193401; year: 2001

Abstract: In a variety of casts the vacancy-adatom pair is shown to be the most widely spread defect on low-index surfaces due to its considerable contribution to the entropy of adatom positions. The results of calculations obtained by the modified embedded-atom and the embedded-atom methods show that the formation energy of the vacancy-adatom pair is slightly less than (or equal to) that of the vacancy for the majority of cases considered.

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Electron momentum distributions for double ionization in the strong field limit

Goreslavski, SP; Popruzhenko, SV; ED Piraux, B; Rzazewski, K

SUPER-INTENSE LASER-ATOM PHYSICS; vol. 12; pp. 41-50; year: 2001

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Structure and direct protonic decay of isobaric analogous and isovector monopole giant resonances

Gorelik, ML; Urin, MH

PHYSICS OF ATOMIC NUCLEI; vol. 64; issue 3; pp. 506-515; year: 2001

Abstract: A description of the partial protonic widths of isobaric analogous resonances is proposed on the basis of the continuum random-phase approximation and a partly self-consistent phenomenological version of the theory of finite Fermi systems. The results of the calculations performed for spherical nuclei over a wide interval of atomic-mass values are in satisfactory agreement with the corresponding experimental widths. The probability of the direct protonic decay of an isovector monopole giant resonance in the beta (-) channel is estimated in connection with some recent experiments.

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Electron-electron correlation in laser-induced nonsequential double ionization

Goreslavskii, SP; Popruzhenko, SV; Kopold, R; Becker, W

PHYSICAL REVIEW A; vol. 64; issue 5; year: 2001

Abstract: The distributions of the momenta of the two electrons liberated in nonsequential double ionization of neon and argon are calculated in the S-matrix formalism assuming a rescattering scenario. Two different forms for the electron-electron correlation are compared: the Coulomb repulsion in the Born approximation and a three-body contact interaction including the ion. The former favors disparate momenta of the two electrons, the latter equal momenta.

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Direct proton-decay properties of the isobaric analog and isovector monopole giant resonances

Gorelik, ML; Urin, MH

PHYSICAL REVIEW C; vol. 63; issue 6; year: 2001

Abstract: A self-consistent shell-model continuum-random-phase approximation approach is developed to evaluate the partial proton widths of isobaric analog resonances in spherical nuclei from a wide mass interval. The results are found to be in reasonable agreement with the experimental data. An attempt to deduce the single-particle spectroscopic factors from the comparison of the experimental and calculated widths is undertaken. The direct proton-decay branching ratio for the isovector giant monopole resonance in Bi-208 is estimated in connection with recent experimental data.

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Semiclassical approximation and 1/n expansion in quantum-mechanical problems

Karnakov, BM; Mur, VD; Popov, VS

PHYSICS OF ATOMIC NUCLEI; vol. 64; issue 4; pp. 670-690; year: 2001

Abstract: The semiclassical approximation and the technique of 1/n expansion are used to calculate the eigenenergies and the wave functions for the radial Schrodinger equation. It is shown that the expressions that are asymptotically exact in the limit n = n(r) + l + 1 --> infinity and which describe the above eigenenergies and the asymptotic coefficients at the origin and at infinity ensure a satisfactory precision even for states characterized by modest values of the quantum numbers II, and I, including the ground state. (C) 2001 MAIK "Nauka/Interperiodica".

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Distribution of the Gamow-Teller strength in Nb-90 and Bi-208

Krasznahorkay, A; Akimune, H; Fujiwara, M; Harakeh, MN; Janecke, J; Rodin, VA; Urin, MH; Yosoi, M

PHYSICAL REVIEW C; vol. 64; issue 6; year: 2001

Abstract: The (He-3,t) charge-exchange reaction has been studied at E(He-3)=450 MeV and angles near 0 degrees on targets of Zr-90 and Pb-208. Fragmentation of the Gamow-Teller (GT) strength into separate components of the particle-hole type has been observed. The distribution of the GT strength in Nb-90 and in Bi-208 has been calculated within the continuum quasiparticle random phase approximation and continuum-random-phase approximation approaches, respectively. These components, especially in Pb-208, could be related with the direct, core polarization, and back-spin-flip Gamow-Teller strength.

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Method of Green's functions and invariance principle in the problem of sputtering of amorphous and polycrystalline targets

Marinyuk, VV; Remizovich, VS

RADIA ON EFFECTS AND DEFECTS IN LIDS; vol. 154; issue 2; pp. 99-122; year: 2001

Abstract: A new approach to the problem of sputtering is proposed, The approach is based on the invariance principle in combination with the method of separation of fluxes. The problem is considered for the case of linear cascades in amorphous materials. An integral equation directly for the function of the sputtered atoms yield (sputtering function) is found. The cases of both self-sputtering and sputtering by arbitrary ions are investigated. The use of the method of Green's functions allows to construct a regular procedure for solving the integral equations obtained. To illustrate the approach proposed, we calculate the Green's function and the first partial sputtering function for the case of self-sputtering in the approximation of backward collisions. For the hard-spheres scattering, the angular distributions of sputtered atoms are calculated in the quasi single-collision approximation.

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The effect of inelastic loss on the development of interatomic collision cascades

Marinyuk, VV; Remizovich, VS

TECHNICAL PHYSICS; vol. 46; issue 10; pp. 1235-1241; year: 2001

Abstract: A theory of interatomic collision cascades in an infinite medium subject to inelastic energy loss (ionization slowdown) of particles is developed. Emphasis is on the angular and energy distributions of primary ions and cascade atoms upon slowdown. Analysis is performed under the assumption that single scattering of the particles follows the hard ball law, and the electronic stopping power of the medium is determined by the Lindhard formula. It is shown that the inclusion of slowdown directly in solving the Boltzmann transport equation radically changes the angular and energy spectra of the ions and cascade atoms obtained when the slowdown is ignored. Moreover, slowdown is the factor responsible for the anisotropy of the angular distributions of low-energy primary ions and cascade atoms. (C) 2001 MAIK "Nauka/Interperiodica".

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Energy and momentum spectra of photoelectrons under conditions of ionization by strong laser radiation (the case of elliptic polarization)

Mur, VD; Popruzhenko, SV; Popov, VS

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 92; issue 5; pp. 777-788; year: 2001

Abstract: Analytical and numerical studies are made into the momentum distribution and energy spectra of photoelectrons emitted during nonlinear ionization of atoms and molecules by laser radiation with elliptic polarization. The dependence of these distributions on the ellipticity xi of an electromagnetic wave is treated, as well as their evolution upon variation of the Keldysh parameter gamma from the region of optical tunneling (gamma << 1) to the region of gamma >> 1, in which the ionization is multiphoton. The quasiclassical approximation is used in the calculations, in particular, the imaginary-time method and the saddle-point method with expansion in the vicinity of the field ellipse. (C) 2001 MAIK "Nauka/Interperiodica".

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Dynamical Lamb effect versus dynamical Casimir effect

Narozhny, NB; Fedotov, AM; Lozovik, YE

PHYSICAL REVIEW A; vol. 64; issue 5; year: 2001

Abstract: An atom interacting with a quantized electromagnetic field in a cavity with time-dependent parameters is considered, Variation of the cavity parameters results in nonstationary dynamics of the field which leads, in turn. to excitation of the atom, even if photons were initially absent in the cavity. We distinguish three mechanisms of such excitation: excitation due to absorption of real photons created by the dynamical Casimir effect, excitation due to absorption of virtual photons during the transient process, and excitation due to nonadiabatic parametric modulation of the atomic Lamb shift. The last mechanism has no relation to the dynamical Casimir effect and thus should be considered as a new vacuum QED effect. Normally all these three mechanisms give a contribution to the amplitude of the atom excitation and are accompanied by the creation of photons. Therefore the presence of an atom in the cavity alters the average number of created photons in comparison with the case of an empty non-stationary cavity. Our consideration is based mainly on a simple model of a two-level atom interacting with a single mode of quantized electromagnetic field. However, our results are qualitatively valid for more realistic models.

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About new method of high harmonic amplification

Nersesov, EA; Popruzhenko, SV; Zaretsky, DF; Piraux, B; Rzazewski, K

SUPER-INTENSE LASER-ATOM PHYSICS; vol. 12; pp. 259-263; year: 2001

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Amplification of high-order harmonies in a short laser pulse by stimulated interaction

Nersesov, EA; Popruzhenko, SV; Zaretsky, DF; Becker, W; Agostini, P

PHYSICAL REVIEW A; vol. 64; issue 2; pp. art. no.-023419; year: 2001

Abstract: The case is considered of a weak Gaussian harmonic pulse of frquency (2s + 1) omega passed through an atomic medium collinearly with an intense Gaussian laser pulse of frequency omega. The harmonic beam may be amplified or deamplified according to the balance between stimulated emission and absorption. A simple analytic expression for the gain is derived in the tunneling limit of ionization. It predicts a positive (negative) gain for positive (negative) delay of the harmonic pulse with respect to the laser pump pulse. The gain may be significant and proportional to the delay for delays of a few laser periods, much shorter than the pulse envelopes. Possibilities for experimental observations are briefly discussed.

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Photoelectron momentum distribution for double ionization in strong laser fields

Popruzhenko, SV; Goreslavskii, SP

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OP CAL PHYSICS; vol. 34; issue 8; pp. L239-246; year: 2001

Abstract: Non-sequential double ionization of atoms in a strong Linearly polarized laser field is studied on the basis of the generalized Keldysh model. The transition amplitude is calculated using a saddle-point method and the distribution in the total and relative momenta of two emitted electrons is found in an analytical form. The obtained result is compared with that from the simple-man approach. By integrating over the relative momentum we calculate the distribution in the total momentum. Its shape with two maxima and their positions are in good agreement with recent experimental measurements and elaborate numerical calculations of the recoil momentum distribution for doubly charged ions. We show that positions of the maxima depend strongly on the differential cross section of (e --> 2e) inelastic collisions.

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Direct-decay properties of charge-exchange spin giant resonances

Rodin, VA; Urin, MH

NUCLEAR PHYSICS A; vol. 687; issue 1-2; pp. 276C-281; year: 2001

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Nonlinear Doppler-shifted cyclotron resonance in aluminum

Skobov, VG; Chernov, AS

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 92; issue 2; pp. 338-344; year: 2001

Abstract: The Doppler-shifted cyclotron resonance in an aluminum plate in the geometry when constant magnetic field H is directed along the [100] crystallographic axis oriented normally to the surface of the plate is studied theoretically. The analysis is performed for a simple model Fermi surface possessing fourth-order symmetry. Capture of holes by the magnetic field of a radio-frequency wave is shown to considerably decrease the effectiveness of cyclotron absorption at large exciting field amplitudes. This suppresses the collisionless damping of dopplerons (propagating modes related to odd cyclotron resonance harmonics). As a result, the sample becomes more transparent to radio-frequency radiation. (C) 2001 MAIK "Nauka/Interperiodica".

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Structure of the 11/2(-) analog state in Nb-91 populated by the Zr-90(alpha, t) reaction

van der Molen, HKT; Akimune, H; van den Berg, AM; Daito, I; Fujimura, H; Fujita, Y; Fujiwara, M; Harakeh, MN; Ihara, F; Inomata, T; Ishibashi, K; Janecke, J; Kalantar-Nayestanaki, N; Laurent, H; Lhenry, I; O'Donnell, TW; Rodin, VA; Tamii, A; Toyokawa, H; Urin, MH; Yoshida, H; Yosoi, M

PHYSICS LETTERS B; vol. 502; issue 1-4; pp. 1-8; year: 2001

Abstract: Decay via proton emission of isobaric analog states (IAS's) in Nb-91 was studied using the Zr-90(alpha, t) reaction at E-alpha = 180 MeV. This study provides information about the damping mechanism of these states. Decay to the ground state and low-lying phonon states in 90Zr was observed. The experimental data are compared with theoretical predictions wherein the IAS 'single-particle' proton escape widths are calculated in a continuum RPA approach. The branching ratios for decay to the phonon states are explained using a simple model. (C) 2001 Published by Elsevier Science B.V.

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Collective and single-particle states at high excitation energy

van den Berg, AM; Akimune, H; Daito, I; Fujimura, H; Fujiwara, M; Fujita, Y; Harakeh, MN; Ihara, F; Inomata, T; Ishibashi, K; Janecke, J; Kalantar-Nayestanaki, N; Laurent, H; Lhenry, I; van der Molen, HKT; O'Donnell, T; Rodin, VA; Tamii, A; Toyokawa, H; Urin, MH; Yoshida, H; Yosoi, M

ACTA PHYSICA HUNGARICA NEW SERIES-HEAVY ION PHYSICS; vol. 13; issue 1-3; pp. 21-30; year: 2001

Abstract: Damping of high-lying single-particle states was investigated by the study of decay by proton emission from high-lying states in Nb-91, populated by the Zr-90(alpha, t) reaction at E-alpha = 180 MeV. In addition to decay to the ground state of Zr-90, semi-direct decay was observed to the low-lying (2(+)/5(-) and 3(-)) phonon states, confirming the conclusion from other experiments that phonon states play an important role in the damping process of the single-particle states. Furthermore, the population and decay of isobaric analogue states of Zr-91, which are located at an excitation energy of about 10 - 12 MeV in Nb-91, has been studied in the same reaction.

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On the possibility of increasing the intensity of high-order harmonics due to stimulated emission

Zaretskii, DF; Nersesov, EA; Popruzhenko, SV; Becker, W

LASER PHYSICS; vol. 11; issue 5; pp. 616-619; year: 2001

Abstract: We propose a new method for the amplification of high-order harmonics of laser radiation based on stimulated emission accompanying the propagation of a probe pulse of a high-order harmonic through a gas medium irradiated by a high-power pump wave. It is demonstrated that such an amplification becomes noticeable in the case when a probe wave of a high-order harmonic enters the interaction area with some delay time with respect to the pump wave. Our estimates for the gain of high-order harmonics show that this gain is proportional to the delay time, reaching unity even for rather short delay times (corresponding to several optical cycles of the pump wave).

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Properties of the isoscalar giant dipole resonance

Gorelik, ML; Urin, MH

PHYSICAL REVIEW C; vol. 64; issue 4; year: 2001

Abstract: The main properties (strength function, energy-dependent transition density, branching ratios for direct nucleon decay) of the isoscalar giant dipole resonance in several medium-heavy mass spherical nuclei are described within a continuum random-phase approximation approach, taking into account the smearing effect. All model parameters used in the calculations are taken from independent data. The calculation results are compared with available experimental data.

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Exact conservation laws of the gradient expanded Kadanoff-Baym equations

Knoll, J; Ivanov, YB; Voskresensky, DN

ANNALS OF PHYSICS; vol. 293; issue 2; pp. 126-146; year: 2001

Abstract: It is shown that the Kadanoff-Baym equations at consistent first-order gradient approximation reveal exact rather than approximate conservation laws related to global symmetries of the system. The conserved currents and energy-momentum tensor coincide with corresponding Noether quantities in the local approximation. These exact conservations are valid, provided a cl) derivable approximation is used to describe die system, and possible memory effects in the collision term are also consistently evaluated up to first-order gradients. (C) 2001 Academic Press.

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Point defects at low-index surfaces of fee metals and the anomalous behaviour of surface atoms at elevated temperatures

Devyatko, YN; Rogozhkin, SV

VACUUM; vol. 56; issue 4; pp. 279-285; year: 2000

Abstract: We have demonstrated that, taking into consideration the presence of surface defects (vacancies and adatoms), the enhanced amplitudes of atom vibrations on metal surfaces at moderate and high temperatures can be described. The model has allowed the formation energy of point defects and the Debye temperature for surfaces with various orientations to be deduced. By the modified embedded-atom method (MEAM), we have calculated the formation energies of the isolated vacancy and the vacancy-adatom pair. The results predict the prevailing formation of pairs on the surfaces (1 1 0) and (1 0 0). With good accuracy, the calculated energy values coincide with those obtained from experiments. (C) 2000 Elsevier Science Ltd. All rights reserved.

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Photoionization with rescattering: Quantum theory and the semiclassical approach

Goreslavskii, SP; Popruzhenko, SV

LASER PHYSICS; vol. 10; issue 2; pp. 583-587; year: 2000

Abstract: We compare the spectral-angular distributions of photoelectrons in a high-energy plateau of above-threshold ionization calculated in the tunneling limit within the framework of a semiclassical three-step model and obtained by the saddle-point method. It is demonstrated that both procedures of calculations give mathematically equivalent results, adequately describing the distribution of photoelectrons within the range predicted by the three-step model, but become inapplicable near the boundaries of this range.

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Tunneling limit in the theory of photoelectron rescattering by the parent ion

Goreslavskii, SP; Popruzhenko, SV

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 90; issue 5; pp. 778-787; year: 2000

Abstract: A generalized Keldysh model is used to obtain simple analytical expressions for the energy and angular distributions of photoelectrons rescattered by the parent ion. The dependence of the form, absolute magnitude, and interference structure of the distributions on the parameters of the field and atom is investigated. It is shown that even though the semiclassical three-step rescattering model determines correctly the position of the boundaries beyond which the distributions decay rapidly, the model itself is inapplicable near them. (C) 2000 MAIK "Nauka/Interperiodica".

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Structure and direct nucleon decay properties of isoscalar giant monopole and dipole resonances

Gorelik, ML; Shlomo, S; Urin, MH

PHYSICAL REVIEW C; vol. 62; issue 4; year: 2000

Abstract: The strength function and partial widths for the direct nucleon decay of the isoscalar giant monopole and dipole resonances are analyzed within an extended continuum-random-phase-approximation approach. Calculations are performed for several medium and heavy mass nuclei with the use of a phenomenological nuclear mean field, the Landau-Migdal particle-hole interaction, and some partial self-consistency conditions. Calculation results are compared with available experimental data.

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Propagation of a narrow beam of polarized light in a random medium with large-scale inhomogeneities

Gorodnichev, EE; Kuzovlev, AI; Rogozkin, DB

LASER PHYSICS; vol. 10; issue 6; pp. 1236-1243; year: 2000

Abstract: The Rytov rotation of the polarization plane is considered for narrow beam propagation through a random medium with large (larger than the wavelength) inhomogeneities. Multiple scattering of light is assumed to be strongly anisotropical. With the "geometrical" approximation, a solution to the vector radiative transfer equation is found.

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Changes in positron quasi-particle during interaction of the positron with metal surface

Gusarov, IA; Korovushkin, AV; Osadchiev, VM

IZVESTIYA AKADEMII NK SERIYA FIZICHESKAYA; vol. 64; issue 4; pp. 782-786; year: 2000

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Resonance transport and kinetic entropy

Ivanov, YB; Knoll, J; Voskresensky, DN

NUCLEAR PHYSICS A; vol. 672; issue 1-4; pp. 313-356; year: 2000

Abstract: We continue the description of the dynamics of unstable particles within the real-time formulation of nonequilibrium field theory initiated in a previous paper [1]. There we suggest to use Baym's Phi-functional method in order to achieve approximation schemes with 'built in' consistency with respect to conservation laws and thermodynamics even in the case of particles with finite damping width. Starting from Kadanoff-Baym equations we discuss a consistent first order gradient approach to transport which preset-yes the Phi-derivable properties. The validity conditions for the resulting quantum four-phase-space kinetic theory are discussed under the perspective to treat particles with broad damping widths. This non-equilibrium dynamics naturally includes all those quantum features already inherent in the corresponding equilibrium limit (e.g. Matsubara formalism) at the same level of Phi-derivable approximation. Various collision-term diagrams are discussed including those of higher order which lead to memory effects. As an important novel part we derive a generalized nonequilibrium expression for the kinetic entropy flow, which includes contributions from fluctuations and mass-width effects. In special cases an ii-theorem is derived implying that the entropy can only increase with time. Memory effects in the kinetic terms provide contributions to the kinetic entropy flow that in the equilibrium limit recover the famous bosonic type T-3 ln T correction to the specific heat in the case of Fermi liquids like Helium-3. (C) 2000 Elsevier Science B.V. All rights reserved.

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Contributions of the inward and backward ion fluxes to sputtering at the grazing incidence of the beam

Kurnaev, VA; Marinyuk, VV; Remizovich, VS; Trifonov, NN

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SEC ON B-BEAM INTERAC ONS WITH MATERIALS AND ATOMS; vol. 164; pp. 848-853; year: 2000

Abstract: Two mechanisms of the recoil sputtering are investigated. The first one is connected with recoils generated by the inward flux of incoming ions while the second one - with those generated by the backward flux of ions reflected from the bulk of the target. It is shown analytically that the ratio of the yields given by the two mechanisms is equal to 2 and does not depend on the energy and direction of the recoil emission, the angle of incidence and energy of primary ions, the atomic masses of the projectile and the target atom. Computer simulations for 1-30 keV Ar ions incident on Pt target at grazing angles are rather in good agreement with the analytical theory. (C) 2000 Elsevier Science B.V. All rights reserved.

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Use of the invariance principle in the theory of sputtering of amorphous and polycrystal materials

Marinyuk, VV; Remizovich, VS

IZVESTIYA AKADEMII NK SERIYA FIZICHESKAYA; vol. 64; issue 4; pp. 777-781; year: 2000

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Depth distribution of light ions under grazing incidence on a target

Marinyuk, VV; Remizovich, VS

TECHNICAL PHYSICS; vol. 45; issue 9; pp. 1105-1109; year: 2000

Abstract: The depth distribution of light ions under grazing incidence on the surface of a semi-infinite layer was analytically derived. It was assumed that the interaction between the ions and atoms of the medium is described by potentials in the form of an inverse power function: (V(r) similar to r(-1/nu)). Calculations showed that the ion distribution (ion density) peaks at some depth, rather than being a monotonic function. The more slowly the potential decreases (the larger the value of nu), the more distinct the ion density peak and the deeper its position. At large depths, the ion density drops according to a power law. (C) 2000 MAIK "Nauka/ Interperiodica".

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The rate of the 2 nu beta beta-decay of Ca-48

Mazepa, EV; Rumyantsev, OA; Urin, MH

IZVESTIYA AKADEMII NK SERIYA FIZICHESKAYA; vol. 64; issue 3; pp. 511-514; year: 2000

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Quantum processes in a two-mode laser field

Narozhny, NB; Fofanov, MS

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 90; issue 3; pp. 415-427; year: 2000

Abstract: The probabilities of the emission of a photon by an electron and e(+)e(-)-pair photoproduction in a field which is a superposition of two electromagnetic plane waves with different frequencies and propagating in the same direction are obtained. The case where the frequencies of the two modes are commensurate is studied in detail. This case is interesting primarily because of the existence of effects due to the interference of amplitudes, corresponding to a different number of photons absorbed from different modes but having the same total 4-momentum. It is shown that the optimal field for observing interference effects is a field such that the ratio of the mode frequencies is 3. The probabilities of radiation and pair-photoproduction processes in the field of a monochromatic plane wave and in a two-mode field, obtained by splitting the initial wave into two waves, are compared. It is shown that the total probability of the emission of a photon by an electron in a two-mode field is lower than and the probability of pair photoproduction is higher than the probabilities of the same processes in the initial wave. The increase in the pair-photoproduction probability is explained by the fact that additional channels for reactions which are forbidden in the initial monochromatic field open up in a two-mode field. (C) 2000 MAIK "Nauka/Interperiodica".

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Scattering of relativistic electrons by a focused laser pulse

Narozhny, NB; Fofanov, MS

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 90; issue 5; pp. 753-768; year: 2000

Abstract: The problem of the motion of a classical relativistic electron in a focused high-intensity laser pulse is solved. A new three-dimensional model of the electromagnetic field, which is an exact solution of Maxwell's equations, is proposed to describe a stationary laser beam. An extension of the model is proposed. This extension describes a laser pulse of finite duration and is an approximate solution of Maxwell's equations. The equations for the average motion of an electron in the field of a laser pulse, described by our model, are derived assuming weak spatial and temporal nonuniformities of the field. It is shown that, to a first approximation in the parameters of the nonuniformities, the average (ponderomotive) force acting on a particle is described by the gradient of the ponderomotive potential, but it loses its potential character even in second order. It is found that the three-dimensional ponderomotive potential is asymmetric. The trajectories of relativistic electrons moving in a laser field are obtained and the cross sections for scattering of electrons by a stationary laser beam are calculated. It is shown that reflection of electrons from the laser pulse and the surfing effect are present in the model studied. It is found that for certain impact parameters of the incident electrons the asymmetic ponderomotive potential can manifest itself effectively as an attractive potential. It is also shown that even in the case of a symmetric potential the scattering cross section contains singularities, known as rainbow scattering. The results are applicable for fields characterized by large (compared to 1) values of the dimensionless parameter eta(2) = e(2)[E-2]/m(2)omega(2) and arbitrary electron energies. (C) 2000 MAIK "Nauka/Interperiodica".

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The method of partial fluxes: Reflection of optical radiation from a semi-infinite homogeneous medium with a trinomial phase function

Remizovich, VS; Radkevich, AV

LASER PHYSICS; vol. 10; issue 2; pp. 560-575; year: 2000

Abstract: This paper continues the analysis of the problem of light reflection from a semi-infinite dissipative medium. Using the method of flux separation, we perform an analytical calculation of the first partial reflection function S-(1) integrated over the azimuthal angle in the case when the expansion of the scattering phase function in spherical harmonics involves three Legendre polynomials. The phase functions corresponding to isotropic and Rayleigh scattering of light from random scattering centers are particular cases of the phase function of the considered type. The first partial reflection function S-(1) describes the angular distribution of photons that escape from the medium reversing the sign of their velocity projections on the direction of the inner normal only once. In the case of the normal incidence of radiation on the surface of a medium, the first partial reflection function is compared with the total reflection function S, obtained by the numerical solution of the relevant nonlinear integral equation. We analyze the influence of the parameters of the scattering phase function on the accuracy of the S-(1) approximation. It is demonstrated that the first partial reflection function adequately describes even some specific features in the spectrum of reflected radiation, including local maxima and inflection points. For media with strong absorption, the quantities S and S(1) are shown to coincide with each other with an accuracy up to several percent. For media with weak absorption, the remaining part of reflected radiation (i.e., S - S-(1)), which is associated with photons that reverse the sign of their velocity projections on the direction of the inner normal to the surface of the medium three and more times, is described by a dependence close to a cosine function.

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Relationship between the doubly angular Green's function of the Ambartsumyan equation and spatial-angular Green's functions of the transfer equation: Symmetry relations

Remizovich, VS; Radkevich, AV

LASER PHYSICS; vol. 10; issue 3; pp. 820-826; year: 2000

Abstract: The problem of reflection of scalar optical radiation from random media is considered. We analyze two aspects of determining the angular spectrum of backscattered radiation related to the solution of the transfer equation with the method of flux separation and the calculation of the reflection function of photons directly from the Ambartsumyan equation with the use of the invariance principle. We derive the relation between the spatial-angular Green's functions of the transfer equation and doubly angular Green's functions of the Ambartsumyan equation for an arbitrary law of single scattering and arbitrary absorption of a medium. The symmetry properties of spatial-angular Green's functions in the linear theory of transfer of optical radiation are determined, and the symmetry properties of all the partial reflection functions are specified.

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On the neutron radiative capture in the vicinity of the giant dipole resonance

Rodin, VA; Urin, MH

PHYSICS LETTERS B; vol. 480; issue 1-2; pp. 45-52; year: 2000

Abstract: A semimicroscopical approach is applied for describing partial photonucleon reactions accompanying the excitation of the giant dipole resonance (GDR). The approach is based on continuum-RPA and the phenomenological description of doorway-state coupling to many-quasiparticle configurations. Apart from the phenomenological mean field, the separable isovector momentum-dependent forces are taken into consideration together with the momentum-independent Landau-Migdal interaction. It allows us to describe satisfactorily the experimental values of the GDR energy and the photoabsorption cross section integrated over the GDR in Pb-208 along with some partial Pb-208(n,gamma)-reaction cross sections in the vicinity of the GDR. An attempt to establish a correspondence between the approach and the well-known DSD-model was also undertaken. (C) 2000 Elsevier Science B.V. All rights reserved.

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On the neutron radiative capture in the vicinity of the giant dipole resonance

Rodin, VA; Urin, MH; Wender, S

CAPTURE GAMMA-RAY SPECTROSCOyear: AND RELATED TOPICS; vol. 529; pp. 165-172; year: 2000

Abstract: A semimicroscopical approach is applied for describing partial photonucleon reactions accompanied by excitation of the giant dipole resonance (GDR). The approach is based on the continuum-RPA and phenomenological description of the doorway-state coupling to many-quasiparticle configurations. Apart from the phenomenological mean field, the separable isovector momentum-dependent forces are taken into consideration together with the momentum-independent pal-tide-hole interaction. It allows us to describe satisfactorily the experimental values of the GDR energy and the photoabsorption cross section integrated over GDR in Pb-208 along with some partial Pb-208(n gamma)- reaction cross sections in the vicinity of the GDR. An attempt to establish a correspondence between the approach and the well-known DSD-model was also undertaken.

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On the hindrance of the two-neutrino beta beta-decay rate

Rumyantsev, OA; Urin, MH

CZECHOSLOVAK JOURNAL OF PHYSICS; vol. 50; issue 4; pp. 529-535; year: 2000

Abstract: A nonstandard approach for describing the nuclear 2 nu beta beta decay is briefly outlined and applied to the decay of Ca-48. The approach is based on a new formula obtained by a model-independent transformation of the known expression for the amplitude. This formula takes explicitly into account hindrance of the decay-amplitude due to the presence of the collective Gamow-Teller state. Calculation results are compared with known experimental data.

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'Shaking' of an atom in a non-stationary cavity

Fedotov, AM; Narozhny, NB; Lozovik, YE

PHYSICS LETTERS A; vol. 274; issue 5-6; pp. 213-222; year: 2000

Abstract: We consider an atom interacting with a quantized electromagnetic field inside a cavity with variable parameters. The atom in the ground state located in the initially empty cavity can be excited by variation of cavity parameters. We have discovered two mechanisms of atomic excitation. The first arises due to the interaction of the atom with the non-stationary electromagnetic field created by modulation of cavity parameters. If the characteristic time of variation of cavity parameters is of the order of the atomic transition time, the processes of photon creation and atomic excitation are going on simultaneously and hence excitation of the atom cannot be reduced to trivial absorption of the photons produced by the dynamical Casimir effect. The second mechanism is 'shaking' of the atom due to fast modulation of its ground state Lamb shift which takes place as a result of fast variation of cavity parameters. The last mechanism has no connection with the vacuum dynamical Casimir effect. Moreover, it opens a new channel of photon creation in the non-stationary cavity. Nevertheless, the process of photon creation is altered by the presence of the atom in the cavity, even if one disregards the existence of the new channel. In particular, it removes the restriction for creation of only even number of photons and also changes the expectation value for the number of created photons. Our consideration is based on a simple model of a two-level atom interacting with a single mode of the cavity field. Qualitatively our results are valid for a real atom in a physical cavity. (C) 2000 Elsevier Science B.V. All rights reserved.

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E1 transitions between spin-dipole and Gamow-Teller giant resonances

Rodin, VA; Urin, MH

PHYSICAL REVIEW C; vol. 62; issue 6; year: 2000

Abstract: The branching ratios for E1 transitions between the spin-dipole (SD) and Gamow-Teller (GT) giant resonances in Nb-90 and Pb-208 are evaluated. Assuming the main GT state has a wave function close to that for the "ideal" GT state, we reduced the problem to calculate the SD and GT strength functions. These strength functions are evaluated within an extended continuum-random phase approximation approach.

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Structure and decay properties of the isoscalar giant monopole and dipole resonances within a continuum-RPA approach

Gorelik, ML; Urin, MH; Shlomo, S; ED Oganessian, YT; Kalpakchieva, R

NUCLEAR SHELLS - 50 YEARS; pp. 429-438; year: 2000

Abstract: Strength function and partial widths for the direct nucleon decay of the isoscalar giant monopole and dipole resonances are analyzed within a continuum-RPA approach. Calculations are performed for several medium and heavy mass nuclei with the use of the phenomenological nuclear mean field, Landau-Migdal particle-hole interaction and some partial self-consistency conditions. Calculation results are compared with available experimental data.

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Rate of the 2 nu beta beta-decay of Ca-48

Mazepa, EV; Rumyantsev, OA; Urin, MH; ED Oganessian, YT; Kalpakchieva, R

NUCLEAR SHELLS - 50 YEARS; pp. 439-443; year: 2000

Abstract: Within the framework of a nonstandard approach a simple formula for the nuclear amplitude of the Z nu beta beta -decay of Ca-48 is obtained. The hindrance of the 2 nu beta beta -decay rate caused by the presence of the collective Gamow-Teller state is explicitly taken into account within the approach. Calculation results are compared with known experimental data.

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On the neutron radiative capture in the vicinity of the giant dipole resonance

Rodin, VA; Urin, MH; ED Dang, ND; Arima, A

INTERNA ONAL SYMPOSIUM ON QUASIPAR CLE AND PHONON EXCITA ONS IN NUCLEI (LOVIEV 99); pp. 211-218; year: 2000

Abstract: A semimicroscopical approach is applied for describing partial photonucleon reactions accompanied by excitation of the giant dipole resonance (GDR). The approach is based on the continuum-RPA and phenomenological description of the doorway-state coupling to many-quasiparticle configurations. Apart from the phenomenological mean field, the separable isovector momentum-dependent forces are taken into consideration together with the momentum-independent particle-hole interaction. It allows us to describe satisfactorily the experimental values of the GDR energy and the photoabsorption cross section integrated over GDR in (208)pb along with some partial Pb-208(n gamma)- reaction cross sections in the vicinity of the GDR. An attempt to establish a correspondence between the approach and the well-known DSD-model was also undertaken.

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Vacancy mechanism of the anomalous behavior of surface atoms at elevated temperatures

Devyatko, YN; Rogozhkin, SV; Troyan, VI; Gusev, EP; Gustafsson, T

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 89; issue 6; pp. 1103-1106; year: 1999

Abstract: A model that takes into account the significant contribution of vacancies at moderate and high temperatures is proposed to explain the anomalous increase in the mean-square displacements of atoms in transition-metal surface monolayers. The dependence of the effects on the orientation of the surface is explained. The vacancy formation energies and the values of the Debye temperature are obtained within the proposed model for differently oriented surfaces. (C) 1999 American Institute of Physics. [S1063-7761(99)01212-3].

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Partial proton widths of isobaric analog resonances in spherical nuclei with nucleon coupling

Gorelik, ML; Zvenigorodskij, AG; Rumyantsev, OA; Urin, MH

IZVESTIYA AKADEMII NK SERIYA FIZICHESKAYA; vol. 63; issue 5; pp. 883-888; year: 1999

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The angular distribution of nonlinear Thomson scattering in a circular field

Goreslavskii, SP; Popruzhenko, SV; Shcherbachev, OV

LASER PHYSICS; vol. 9; issue 5; pp. 1039-1044; year: 1999

Abstract: We consider classical emission of a relativistic electron moving in an arbitrary direction with respect to the direction of propagation of a strong circularly polarized electromagnetic wave. The exact expression for the angular distribution is derived by the summation of harmonics in the spectral-angular distribution. The evolution of the symmetry and the shape of this angular distribution is investigated for different initial conditions for an electron and the intensity of the electromagnetic wave.

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Rescattering and quantum interference near the classical cut-offs

Goreslavskii, SP; Popruzhenko, SV

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OP CAL PHYSICS; vol. 32; issue 19; pp. L531-538; year: 1999

Abstract: We present a quantum mechanical derivation of a closed analytic formula which describes the distribution of photoelectrons rescattered by their parent ions and emitted with energies and at angles around the boundaries imposed by the classical rescattering model. The distribution decays smoothly beyond the classical limits and demonstrates an interference structure within these limits.

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Propagation of circularly polarized light in media with large-scale inhomogeneities

Gorodnichev, EE; Kuzovlev, AI; Rogozkin, DB

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 88; issue 3; pp. 421-432; year: 1999

Abstract: Small-angle multiple scattering of circularly polarized waves in disordered systems composed of large (larger than the light wavelength) spherical particles is discussed. The equation for Stokes's fourth parameter V - the difference between the intensities of the left- and right-hand polarized light - is shown to have the form similar to that of the scalar transport equation for intensity I, the only difference being the presence of an additional "non-small-angle'' term responsible for depolarization. In the case of small-angle scattering, depolarizing collisions are relatively rare and, in contrast to the scalar case, the problem contains an additional spatial scale, namely the depolarization depth. The polarization degree and helicity of the scattered light are calculated for the case of purely elastic scattering and in the presence of absorption in the medium. For strong absorption, depolarization is shown to follow the transition to the asymptotic regime of wave propagation. The features appearing in strong (non-Born) single scattering are also discussed. (C) 1999 American Institute of Physics. [S1063-7761(99)00103-1].

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Depolarization of light in small-angle multiple scattering in random media

Gorodnichev, EE; Kuzovlev, AI; Rogozkin, DB

LASER PHYSICS; vol. 9; issue 6; pp. 1210-1227; year: 1999

Abstract: The decay of light linear polarization by multiple scattering in a random medium with large-scale inhomogeneities is considered. The small-angle vector transport equation is derived. The Stokes parameters in the small-angle diffusion approximation are calculated. It is shown that there is a qualitative difference in decay mechanisms for circular and linear polarization: the circular polarization decays much slower than the linear polarization.

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Self-consistent approximations to non-equilibrium many-body theory

Ivanov, YB; Knoll, J; Voskresensky, DN

NUCLEAR PHYSICS A; vol. 657; issue 4; pp. 413-445; year: 1999

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Quasiclassical approximation with the centrifugal potential excluded

Karnakov, BM; Mur, VD; Popov, VS

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 89; issue 2; pp. 271-278; year: 1999

Abstract: We develop a modification of the WKB method (the modified quantization method, or MQM) for finding the radial wave functions. The method is based on excluding the centrifugal potential from the quasiclassical momentum and changing correspondingly the phase in the Bohr-Sommerfeld quantization condition. MQM is used to calculate the asymptotic coefficients at zero and at infinity. We use the examples of power-law and funnel potentials to show that MQM not only dramatically broadens the possibilities of studying the energy spectrum and the wave functions analytically but also ensures accuracy to within a few percent even when one calculates states with a radial quantum number n(r)similar to 1, provided that the angular momentum l is not too large. We also briefly discuss the possibility of generalizing MQM to the relativistic case (the spinless Salpeter equation). (C) 1999 American Institute of Physics. [S1063-7761(99)01108-7].

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Hamiltonian approach to the problem of tunneling of relativistic particles

Karnakov, BM; Mur, VD; Popov, VS

PHYSICS OF ATOMIC NUCLEI; vol. 62; issue 8; pp. 1363-1369; year: 1999

Abstract: The Hamiltonian approach to the problem of tunneling of relativistic particles has been developed. The method is described by applying it to a specific example, the theory of the ionization of a relativistic bound state (whose binding energy is comparable with the electron rest energy mc(2)) under the effect of external electric and magnetic fields. It has been shown that the Hamiltonian approach makes it possible to obtain an explicit expression for both exponential and preexponential factors in the ionization probability.

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Asymptotic coefficients for atoms and ions

Mur, VD; Karnakov, BM; Popov, VS

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 88; issue 2; pp. 286-296; year: 1999

Abstract: We derive convenient analytical formulas in the effective-range approximation for the asymptotic coefficient C (kappa) of the radial wave function at infinity and for the average radius of the system. A comparison with the results of numerical calculations (done by the Hartree-Fock method) for multi-electron atoms and ions reveals that this approximation has good accuracy for valence s-electrons in all atoms from hydrogen to uranium. We calculate the values of the scattering lengths and the effective ranges for electron-atom and electron-ion scattering. We also examine the quasiclassical approximation for C (kappa). Finally, we discuss the logarithmic increase in the effective ranges of ns states as n --> infinity. (C) 1999 American Institute of Physics.

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4h omega isoscalar monopole giant resonance in Pb-208 and resonance trapping

Muraviev, SE; Rotter, I; Shlomo, S; Urin, MH

PHYSICAL REVIEW C; vol. 59; issue 4; pp. 2040-2047; year: 1999

Abstract: Ln the framework of the random phase approximation in the continuum we calculate the strength function of the 4 (h) over bar omega isoscalar monopole giant resonance in Pb-208. The one-particle continuum plays an important role in the formation of the structure of the strength function. Most interesting is the appearance of some narrow resonances at large excitation energy. We discuss the results obtained from the point of view of resonance trapping which is known to appear due to the strong coupling of the resonance states via the continuum. [S0556-2813(9902704-1].

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Comment on "Quantum processes in the field of a two-frequency circularly polarized plane electromagnetic wave"

Narozhny, NB; Fofanov, MS

PHYSICAL REVIEW E; vol. 60; issue 3; pp. 3443-3449; year: 1999

Abstract: We show that there is a mistake in the results recently published by An Yu and Il. Takahashi [Phys., Rev. E 57, 2276 (1998)] for the probabilities of a photon emission by an electron and a pair production by a,photon in the field of a two-frequency plane electromagnetic wave. In this paper we present the corrected expression for the probability of a photon emission which contains terms missed by Yu and Takahashi. We argue also that the effect of presence of the waves with combination frequencies in the external field proposed by the authors of the paper [Phys. Rev. E 57, 2276 (1998)] has no physical basis. [S1063-651X(99)10008-4].

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Lorentz ionization of atoms in a strong magnetic field

Popov, VS; Karnakov, BM; Mur, VD

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 88; issue 5; pp. 902-912; year: 1999

Abstract: Lorentz ionization emerges due to the motion of atoms or ions in a strong magnetic field. We use the semiclassical approximation to calculate the probability w(L) of Lorentz ionization. We also find the stabilization factor S, which takes into account the reduction by the magnetic field of the probability of ionization decay of the bound s state. We estimate the probabilities w(L) in magnetic-cumulation experiments and in astrophysics. We also qualitatively examine the dynamics of the magnetic cumulation process with allowance for the conductivity of the shell. Finally, we discuss a paradox related to the use of the quasistationary solution at the shell expansion stage.(C) 1999 American Institute of Physics. [S1063-7761(99)00905-1].

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Intensity fluctuations in the presence of weak localization of light in a disordered medium

Rogozkin, DB

JETP LETTERS; vol. 69; issue 2; pp. 117-122; year: 1999

Abstract: It is shown that the intensity fluctuations in the speckle pattern arising when light is reflected from a disordered sample are negatively correlated. The relative amplitude of the correlations is two times larger in the exactly backward direction than far from this direction. (C) 1999 American Institute of Physics. [S0021-3640(99)00502-2].

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Nonlinear waves in zinc (vol 87, pg 396, 1998)

Skobov, VG; Chernov, AS

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 88; issue 1; pp. 208-208; year: 1999

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Quantum field aspect of the Unruh problem

Fedotov, AM; Mur, VD; Narozhny, NB; Belinskii, VA; Karnakov, BM

PHYSICS LETTERS A; vol. 254; issue 3-4; pp. 126-132; year: 1999

Abstract: It is shown using a both conventional and algebraic approach to quantum field theory that it is impossible to perform quantization on Unruh modes in Minkowski space-time. Such a quantization implies setting a boundary condition for the quantum held operator which changes the topological properties and symmetry group of space-time and leads to a field theory in two disconnected left and right Rindler space-times. It means that the "Unruh effect" does not exist. (C) 1999 Elsevier Science B.V.

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Strangeness modes in nuclei tested by antineutrinos

Kolomeitsev, EE; Voskresensky, DN

PHYSICAL REVIEW C; vol. 60; issue 3; year: 1999

Abstract: The production of negative strangeness in reactions of inelastic antineutrino scattering on a nucleus provides information on the modification of strange degrees of freedom in nuclear matter. We calculate cross sections of the reaction channels <(nu)over bar>(e(mu)) --> e(+) (mu(+)) + K- and <(nu)over bar>(e(mu)) + p --> Lambda + e(+) (mu(+)) and investigate their sensitivity to the medium effects. In particular, we consider effects induced by the presence of a low-energy excitation mode in the K-spectrum, associated with correlated Lambda-particle and proton-hole states, and by renormalization of the weak interaction in medium. In order to avoid double counting, various contributions to antineutrino scattering are classified with the help of the optical theorem, formulated within the nonequilibrium Green's function technique. [S0556-2813(99)01007-9].

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Structure and decay properties of spin-dipole giant resonances within a semimicroscopical approach

Moukhai, EA; Rodin, VA; Urin, MH

PHYSICS LETTERS B; vol. 447; issue 1-2; pp. 8-14; year: 1999

Abstract: A semimicroscopical approach is applied to calculate: (i) strength functions for the charge-exchange spin-dipole giant resonances in the Pb-208 parent nucleus; (ii) partial and total branching ratios for the direct proton decay of the resonance in Bi-208. The approach is based on continuum-RPA calculations of corresponding reaction-amplitudes and phenomenological description of the doorway-state coupling to many-quasiparticle configurations. The only adjustable parameter needed for the description is found by comparison of the calculated and experimental total widths of the resonance. Other model parameters used in calculations are taken from independent data. The calculated total branching ratio is found to be in reasonable agreement with the experimental value. (C) 1999 Published by Elsevier Science B.V. All rights reserved.

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On the direct nucleon decay of the giant dipole resonance and partial photonucleon reactions

Chekomazov, GA; Urin, MH; Brink, DM; Grypeos, ME; Massen, SE

PROCEEDINGS OF THE EUROPEAN CONFERENCE ON ADVANCES IN NUCLEAR PHYSICS AND RELATED AREAS; pp. 681-685; year: 1999

Abstract: A semi-microscopical approach is proposed to describe quantitatively both the branching ratios for the direct nucleon decay and partial photonucleon reaction cross sections in the vicinity of the giant dipole resonance (GDR) in intermediate and heavy mass nuclei. The approach is based on the continuum-RPA calculations of the reaction amplitudes, evaluation of the energy, partial radiative and nucleon escape widths of the 1(-) doorway states, and phenomenological consideration for the coupling of these states to many-particle configurations in average over the energy. The parameters needed for description of the coupling are chosen by comparison of the calculated and experimental photoabsorption cross sections. The approach is applied to calculate several partial Pb-208(n gamma)-reaction cross sections and the respective branching ratios. The calculation results are compared with corresponding experimental data.

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Theory of line broadening in a quantum cyclotron resonance due to neutral impurities

Andreev, SP; Andreev, AS; Gurvich, YA

LASER PHYSICS; vol. 8; issue 1; pp. 159-163; year: 1998

Abstract: We present the results of our recent theoretical investigations [1, 2] on quantum cyclotron resonance (T much less than h over bar omega(H), omega(H) much less than(H) T is the temperature, omega(H)=eH/m*c is the cyclotron frequency, Delta omega=omega-omega(H) is the frequency detuning, m* is the effective mass, and omega is the frequency of the electric field) in semiconductors with an isotropic energy spectrum of charge carriers scattered by small-size centers with a small radius r(c)(2) much less than l(2)=ch over bar/eH, where I is the magnetic length. The proposed approach does not imply the use of perturbation theory in the interaction of carriers with scatterers. It is demonstrated that the contour of the absorption line in quantum cyclotron resonance (QCR) is described by a universal formula of tau-approximation, which is applicable for any frequency detuning, temperature, and magnetic field strength that meet the QCR conditions. The developed theory allowed us to eliminate significant discrepancies that have existed for a long time between theoretical predictions and the results of experiments on QCR due to neutral impurities with the use of FIR lasers with discharge (H2O and D2O lasers, 220-119 mu m) pumping as sources of electromagnetic waves. Theoretical temperature-field and concentration dependences for the QCR line half-width delta omega(T, H, N)(N is the concentration of impurities) obtained in this paper for the scattering due to small-size neutral donors are compared with the relevant experimental data.

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Trapping of electrons into neutral impurities in semiconductors in a quantizing magnetic field

Andreev, SP; Churyumov, AN

LASER PHYSICS; vol. 8; issue 6; pp. 1208-1217; year: 1998

Abstract: We consider the trapping of electrons into shallow neutral donors with a short-range potential (r(c) much less than l(H), where l(H) = root c (h) over bar/eH is the magnetic length) due to the emission of an acoustic phonon in a semiconductor in the presence of a quantizing magnetic field (T much less than (h) over bar omega(H), where omega(H) is the cyclotron frequency and T is the temperature). It is demonstrated that, when carriers are characterized by an isotropic effective mass and the impurity-compensation degree is sufficiently low, trapping into shallow neutral impurities may dominate over trapping into ionized Coulomb centers. The dependence of the coefficient of carrier trapping on the carrier energy is shown to change as the carrier energy approaches the bottom of some Landau band: the inverse lifetime becomes proportional to the transmission coefficient of a particle through a one-dimensional effective impurity potential averaged over the transverse motion of an electron in the magnetic field. Trapping into small-radius neutral impurities is investigated in the case of a sharply anisotropic mass of carriers. It is demonstrated that, in this case, the carrier lifetime with respect to trapping into magnetic-impurity states of an impurity with a short-range potential oscillates as a function of the magnetic field. The revealed oscillations are periodic in the magnetic field as H-1/4. Th, possibility of the experimental observation of carrier trapping into neutral impurities in fourth-group semiconductors in a quantizing magnetic field with the use of infrared (FIR) lasers is discussed.

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Multiple scattering of light in a 2-D medium with large-scale inhomogeneities: An exactly solvable model and approximate methods of calculation

Bolgov, DI; Remizovich, VS; Rogozkin, DB

LASER PHYSICS; vol. 8; issue 2; pp. 462-470; year: 1998

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Simple quantum theory of the high-energy above-threshold ionization spectrum in the tunneling regime

Goreslavskii, SP; Popruzhenko, SV

PHYSICS LETTERS A; vol. 249; issue 5-6; pp. 477-482; year: 1998

Abstract: We formulate an approximate but consistently quantum mechanical model describing the photoelectron distribution in the plateau region. in an analytical form. On one hand, the model retains a number of constituent parts of the semiclassical rescattering picture, but on the hand it incorporates the interference effects in the distribution. (C) 1998 Elsevier Science B.V.

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Mechanism of rescattering of photoelectrons by the parent ion in the optical tunneling regime

Goreslavskii, SP; Popruzhenko, SV

JETP LETTERS; vol. 68; issue 12; pp. 902-907; year: 1998

Abstract: The interference structure of the angular distributions in the high-energy part of the above-threshold ionization spectrum is calculated. The components of the wave packet of the ionized electron that interfere with one another during the interaction with the parent ion are identified. It is shown that the angular distribution averaged over the interference oscillations is determined mainly by the angular dependence of the effective interaction time. (C) 1998 American Institute of Physics. [S0021-3640(98)00224-2].

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Formation and aging of photoelectron wave packets in the tunneling regime

Goreslavsky, SP; Popruzhenko, SV

LASER PHYSICS; vol. 8; issue 5; pp. 1013-1020; year: 1998

Abstract: The coordinate form of the electron wave function after ionization by a strong low-frequency laser field has been derived in the frame of the Keldysh approximation. The wave function is presented as a superposition of partial wave packets produced on separate optical cycles. A detailed description of the properties of the partial packets is presented in the case of linear polarization.

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Diffusion of circularly polarized light in a disordered medium with large-scale inhomogeneities

Gorodnichev, EE; Kuzovlev, AI; Rogozkin, DB

JETP LETTERS; vol. 68; issue 1; pp. 22-28; year: 1998

Abstract: It is shown that in the presence of diffusion of electromagnetic waves in random media containing large discrete scatterers, circular polarization can persist even after the radiation flux is isotropized. For scattering exactly in the backward direction, this effect is manifested as an increase in the interference contribution to the cross-polarized component of the intensity as the size of the scatterers increases. (C) 1998 American Institute of Physics.

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Langer transformation and modified matching conditions in the WKB method

Karnakov, BM; Mur, VD; Popov, VS

PHYSICS OF ATOMIC NUCLEI; vol. 61; issue 3; pp. 420-431; year: 1998

Abstract: It is shown that the Kramers-Langer matching condition in the WKB method is not asymptotically exact in calculating wave functions in the subbarrier region if the orbital angular momentum is l similar to 1. Modified matching conditions free from this drawback are obtained; they depend on l, on the energy E, and on the small-distance behavior of the potential V(r). The precision of the new matching conditions is studied in calculating the asymptotic coefficients in the wave function at the origin and at infinity. Some regularities in the behavior of the semiclassical spectrum for power-law potentials are considered.

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Long-range correlations upon wave propagation in random media under the conditions of strong internal reflection from their boundaries

Korolev, LV; Rogozkin, DB

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 86; issue 1; pp. 164-176; year: 1998

Abstract: The large-scale behavior of the spatial distribution of radiation in a random medium is investigated under the assumption of strong internal reflection from its boundaries. The qualitative variations of the angular coherent backscattering spectrum and long-range spatial intensity correlations in the transmitted and reflected radiation fluxes are predicted. (C) 1998 American Institute of Physics.

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Contribution of surface roughness of an isotropic solid to low-temperature surface heat capacity

Kosachev, VV

LOW TEMPERATURE PHYSICS; vol. 24; issue 5; pp. 367-372; year: 1998

Abstract: The effect of roughness of the free surface of a semi-infinite isotropic solid on the low-temperature surface heat capacity is studied. The method of modified Green's function las compared with that used by Maradudin, Wallis, and Equiluz (1977) and perturbation theory are used for deriving an analytic expression for the contribution of weak roughness to the low-temperature surface heat capacity, which is a correction to the well-known result obtained by Dupuis, Maze, and Onsager (1960) for the surface heat capacity of a semi-infinite isotropic solid with a plane free boundary. It is proved that the inclusion of roughness of isotropic crystals with optical surfaces increases the surface heat capacity in a wide temperature range (of the order of several kelvins). (C) 1998 American Institute of Physics.

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Refraction of the beam of charged particles during inclined transmission through a thin target

Kuzovlev, AI; Kurnaev, VA; Remizovich, VS; Trifonov, NN

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SEC ON B-BEAM INTERAC ONS WITH MATERIALS AND ATOMS; vol. 135; issue 1-4; pp. 477-481; year: 1998

Abstract: The value of the most probable exit angle of particles theta(mp) transmitted through thin targets at inclined incidence of the beam is investigated both analytically and experimentally. A simple formula for theta(mp) is derived as a function of ion energy, beam and target parameters. It is shown that the value of the most probable exit angle for fixed energy of projectiles can be both greater and lesser than the angle of incidence. For particles with high energy, it is shown that the magnitude of such a "refraction" depends on target thickness deviation, the atomic number of the target and is more pronounced for targets with large atomic numbers Z. The measurements of 10 keV protons transmission through thin carbon foil fitted the theoretical predictions well. (C) 1998 Elsevier Science B.V.

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Effect of the ion beam refraction due to multiple scattering in solids

Kuzovlev, AI; Kurnaev, VA; Remizovitch, VS; Trifonov, NN

IZVESTIYA AKADEMII NK SERIYA FIZICHESKAYA; vol. 62; issue 7; pp. 1483-1485; year: 1998

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Structure and decay properties of SDR within semimicroscopical approach

Moukhai, EA; Rodin, VA; Urin, MH; Sakai, H; Okamura, H; Wakasa, T

INTERNA ONAL SYMPOSIUM ON NEW FACET OF SPIN GIANT RENANCES IN NUCLEI; pp. 312-321; year: 1998

Abstract: A semimicroscopical approach is applied to calculate: (i) strength functions for the charge-exchange spin-dipole giant resonances in the Pb-208 parent nucleus; (ii) partial and total branching ratios for the direct proton decay of the resonance in Bi-208. The approach is based on continuum-RPA calculations of respective reaction-amplitudes and phenomenological description for the coupling of particle-hole-type doorway-states to many-quasiparticle configurations. The only adjustable parameter needed for the description is found by a comparison of the calculated total width of the resonance and experimental one. Other model parameters used in calculations are taken from independent data. The calculated total branching ratio is found to be in reasonable agreement with the experimental value.

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Relativistic version of the imaginary-time formalism

Mur, VD; Karnakov, BM; Popov, VS

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 87; issue 3; pp. 433-444; year: 1998

Abstract: A relativistic version of the quasiclassical imaginary-time formalism is developed. It permits calculation of the tunneling probability of relativistic particles through potential barriers, including barriers lacking spherical symmetry. Application of the imaginary-time formalism to concrete problems calls for finding subbarrier trajectories which are solutions of the classical equations of motion, but with an imaginary time (and thus cannot be realized in classical mechanics). The ionization probability of an s level, whose binding energy can be of the order of the rest energy, under the action of electric and magnetic fields of different configuration is calculated using the imaginary-time formalism. Besides the exponential factor, the Coulomb and pre-exponential factors in the ionization probability are calculated. The Hamiltonian approach to the tunneling of relativistic particles is described briefly. Scrutiny of the ionization of heavy atoms by an electric field provides an additional argument against the existence of the "Unruh effect.'' (C) 1998 American Institute of Physics. [S1063-7761(98)00409-0].

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Relativistic version of the imaginary time method

Popov, VS; Mur, VD; Karnakov, BM

PHYSICS LETTERS A; vol. 250; issue 1-3; pp. 20-24; year: 1998

Abstract: We present the relativistic version of the imaginary time method (ITM). The ionization probability w of the bound state under the action of electric and magnetic fields (for the case when the binding energy E-b is comparable with mc(2)) has been calculated using the ITM. The formulae obtained cover both the ionization of nonrelativistic bound systems (atoms, ions) and the case of E-b = 2mc(2), when w is compared with the probability of electron-positron pair production from vacuum in a strong held. (C) 1998 Published by Elsevier Science B.V.

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Ionization of atoms in electric and magnetic fields and the imaginary time method

Popov, VS; Karnakov, BM; Mur, VD

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 86; issue 5; pp. 860-874; year: 1998

Abstract: A semiclassical theory is developed for the ionization of atoms and negative ions in constant, uniform electric and magnetic fields, including the Coulomb interaction between the electron and the atomic core during tunneling. The case of crossed fields (Lorentz ionization) is examined specially, as well as the limit of a strong magnetic field. Analytic equations are derived for arbitrary fields E and H that are weak compared to the characteristic intraatomic fields. The major results of this paper are obtained using the ''imaginary time" method (ITM), in which tunneling is described using the classical equations of motion but with purely imaginary "time." The possibility of generalizing the ITM to the relativistic case, as well as to states with nonzero angular momentum, is pointed out. (C) 1998 American Institute of Physics. [S1063-7761(98)00405-3].

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Comparative analysis of the propagation of light radiation in 2-D and 3-D media: I. Transmission of light radiation through weakly absorbing media with large-scale scatterers

Remizovich, VS; Volkov, SN

LASER PHYSICS; vol. 8; issue 2; pp. 411-437; year: 1998

Abstract: In this paper, we present a review and comparative analysis of the propagation of scalar laser radiation in disordered 2-D and 3-D media Our main attention is focused on the propagation of radiation in media with large-scale las compared with the wavelength of light) scatterers, when the total scattering angle remains small despite substantially multiple scattering. We analyze only the standard small-angle approximation, when one can neglect fluctuations of the path lengths caused by scattering. Various single-scattering laws (Gaussian, Rutherford, exponential, and others) are considered. The correspondence between the small-angle scattering phase functions in 2-D and 3-D media is revealed. We propose a new two-parameter scattering phase function of the generalized exponential type, which includes exponential and sea-scattering phase functions as particular cases.

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Application of Ambartsumyan invariance principle to problem of reflection of light ions

Remizovich, VS; Tishin, IV

IZVESTIYA AKADEMII NK SERIYA FIZICHESKAYA; vol. 62; issue 4; pp. 770-777; year: 1998

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Reflection of light from a plane-parallel medium with a two-directional scattering phase function in the presence of a reflecting lower boundary

Remizovich, VS; Marinyuk, VV; Tishin, IV

LASER PHYSICS; vol. 8; issue 4; pp. 868-879; year: 1998

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Analytical calculation of the Lambertian part of the spectrum of optical radiation reflected from a semi-infinite disordered medium

Remizovich, VS; Radkevich, AV

LASER PHYSICS; vol. 8; issue 5; pp. 974-984; year: 1998

Abstract: In this paper, we propose a new approach to the calculation of spectra of backscattered optical radiation in the case when a plane scatterer is irradiated with a broad light beam. The proposed approach is based on the Ambartsumyan equation for the reflection function (RF), which provides a detailed description of the angular spectrum of reflected radiation for arbitrary angles of incidence and reflection and arbitrary optical characteristics of the medium. Using the principle of partial fluxes developed earlier, we separate the fraction of photons in the RF that emerge from a medium, having changed the sign of their velocity projection on the normal to the surface of the medium only once (the first partial RF). These photons are responsible for the anisotropy in the spectrum of reflected radiation for an arbitrary relation between the wavelength of the light beam and characteristic sizes of scattering centers. The intensity of the remaining reflected radiation flux, which consists of photons that change the sign of their velocity projection three and more times before they emerge from a medium, is a much smoother function of angular variables, which Follows the Lambertian law with high accuracy. In this paper, we develop and implement a regular method for the calculation of the Lambertian part of reflected radiation that can be applied for an arbitrary law of single scattering of photons from chaotically distributed scattering centers in a medium. We provide a comprehensive analysis of isotropic scattering and derive a simple expression Ear the Lambertian part of reflected radiation in this case. The results of our calculation are compared with predictions of Ambartsumyan-Chandrasekhar theory.

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Application of the method of angular Green's functions and the invariance principle in the linear theory of reflection of optical radiation

Remizovich, VS; Radkevich, AV; Tishin, IV

LASER PHYSICS; vol. 8; issue 5; pp. 985-1003; year: 1998

Abstract: This paper considers the problem of reflection of stationary scalar optical radiation from plane media with disordered scattering centers. We propose a new approach to the calculation of spectra of backscattered radiation combining the Ambartsumyan invariance principle and the method of separated fluxes. The total reflection function (RF) is represented as a series over partial RFs. Each of the partial RFs describes the component of reflected radiation consisting of photons that emerge from a medium changing the sign of their velocity projection in the direction of the interior normal to the surface of the medium a definite number of times. Using the nonlinear Ambartsumyan equation, we derived linear integral equations for partial RFs of any order, which permitted us to use the method of angular Green's functions to sequentially calculate all the partial RFs. We derive an integral equation for the angular Green's function in albedo problems of the theory of transfer of optical radiation. Using the derived equations, we calculate the total and partial reflection coefficients for model media with bidirectional scattering phase functions, which allowed us to verify the identity of the results obtained by different methods. A simple approximate method of "backward collisions" is proposed for the calculation of Green's functions in real 3D media with sharply anisotropic scattering centers. Using this method, we have calculated the first partial RF, which provides the main information concerning the angular spectrum of reflected radiation in strongly absorbing media. The results obtained in this study are compared with the results of calculations performed by other authors.

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Nonlinear waves in zinc

Skobov, VG; Chernov, AS

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 87; issue 2; pp. 396-400; year: 1998

Abstract: A theoretical analysis is made of Doppler-shifted cyclotron resonance in zinc in linear and nonlinear regimes. It is shown that the absence of a threshold for cyclotron absorption by holes makes the doppleron strongly damped or eliminates it for low-amplitude wave-fields. At high amplitudes capture of holes by the magnetic field of the wave suppresses collisionless absorption and the doppleron can propagate. As a result, the impedance of the plate is an oscillating function of the magnetic field. It is shown that the effect should be observed at frequencies of the order of a few tens of kilohertz, in magnetic fields of the order of a few kilogauss, and for exciting field amplitudes of the order of a few tens of gauss. (C) 1998 American Institute of Physics. [S1063-7761(98)02708-5].

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Description of the direct nucleonic decay of single-particle quasistationary states of near-magic nuclei within the generalized optical model

Urin, MH; Chekomazov, GA

PHYSICS OF ATOMIC NUCLEI; vol. 61; issue 3; pp. 375-386; year: 1998

Abstract: A method for describing the direct nucleonic decay of single-particle quasistationary states of near-magic nuclei is proposed and applied to some specific examples. The method is based on the optical model generalized to take into account channel coupling. The relative intensities of the decay of some single-particle quasistationary states of the Zr-91, Pb-209 Nb-91, and Bi-209 nuclei to the ground state and some low-lying (single-phonon) states of the product Zr-90 and Pb-208 nuclei are calculated by using the optical-potential parameters determined from analysis of nucleon-nucleus scattering. The results of the calculations for neutronic decay are compared with corresponding experimental data obtained from analysis of cross sections for one-nucleon-transfer reactions.

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Comparative analysis of the propagation of light radiation in 2D and 3D media: II. Transmission of light radiation through strongly absorbing media with large-scale scatterers

Volkov, SN; Remizovich, VS

LASER PHYSICS; vol. 8; issue 6; pp. 1140-1162; year: 1998

Abstract: In this paper, we present a review and comparative analysis of the propagation of scalar light radiation in disordered two- and three-dimensional media. Our main attention is focused on the propagation of radiation in media with large-scale (as compared with the wavelength of light) scatterers, when single scattering of photons is sharply anisotropic. In our analysis, we employ the method of separation of the total light flux into partial fluxes (method of partial fluxes), so that the nth partial flux describes the photons that change the sign of their velocity projection on the interior normal to the surface of a medium exactly n times. The anisotropic part of the light flux (the zeroth partial flux) in 2D and 3D media is calculated with the use of the standard small-angle approximation, when one can neglect the mutual influence of scattering and absorption processes. For the intensity of radiation in a 3D medium, we derive a relationship that extends the Moliere distribution to the case of oblique incidence. We also reveal relation between the intensities of radiation in 2D and 3D media calculated in the standard small-angle approximation. Within the framework of the Fokker-Planck approximation (diffusion approximation in angular variables), we calculate the anisotropic part of the flux corresponding to the small-angle approximation in strongly absorbing 2D media, when the mutual influence of scattering and absorption processes changes the position of the maximum of radiation intensity as a function of depth (rotation of the brightness body). Transmission of Light radiation through strongly absorbing 2D media for large depths (the regime of large depths) is investigated. We calculate and analyze the variance of the angular distribution of photons, the mean path of photons in a medium, and the mean cosine of the scattering angle of photons as a function of the incidence angle and optical characteristics of the medium.

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The strength of the analog and Gamow-Teller giant resonances and hindrance of 2 nu beta beta-decay rate

Rumyantsev, OA; Urin, MH

PHYSICS LETTERS B; vol. 443; issue 1-4; pp. 51-57; year: 1998

Abstract: An approach for describing the hindrance of the nuclear 2 upsilon beta beta-decay amplitude is proposed. The approach is based on a new formula obtained by a model-independent transformation of the initial expression for the amplitude. This formula takes explicitly into account the hindrance of the decay-amplitude due to the presence of the collective Gamow-Teller state. Calculations are pel formed within the simplest version of the approach. Calculated and experimental 2 upsilon beta beta halve-lives are compared for a wide range of nuclei. (C) 1998 Elsevier Science B.V. All rights reserved.

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Contribution of the massive photon decay channel to neutrino cooling of neutron stars

Voskresensky, DN; Kolomeitsev, EE; Kampfer, B

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 87; issue 2; pp. 211-217; year: 1998

Abstract: We consider massive photon decay reactions via intermediate states of electron-electron-holes and proton-proton-holes into neutrino-antineutrino pairs in the course of neutron star cooling. These reactions may become operative in hot neutron stars in the region of proton pairing where the photon due to the Higgs-Meissner effect acquires an effective mass m(gamma) that is small compared to the corresponding plasma frequency. The contribution of these reactions to neutrino emissivity is calculated; it varies with the temperature and the photon mass as T(3/2)m(gamma)(7/2) exp(-m(gamma)/T) for T < m(gamma). Estimates show that these processes appear as extra efficient cooling channels of neutron stars at temperatures T =10(9)-10(10) K. (C) 1998 American Institute of Physics. [S1063-7761(98)00108-5].

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The role of magnetic-impurity states in the broadening of a quantum cyclotron resonance line

Andreev, AS; Andreev, SP; Gurvich, YUA

LASER PHYSICS; vol. 7; issue 2; pp. 488-501; year: 1997

Abstract: A critical role of magnetic-impurity (MI) states of an electron in the presence of an impurity potential with a small radius r(c) (r(c)(2) much less than l(2) = c (h) over bar/eH, l is the magnetic length) in the broadening of a quantum cyclotron resonance (QCR) line is revealed. In the approximation of effective mass, we develop QCR theory for semiconductors with isotropic and sharply anisotropic spectra of charge carriers without using perturbation theory in the interaction of charge carriers with small scrattering centers of r(c2) much less than l(2). A universal formula of tau-approximation that describes an absorption QCR line for any frequency detuning, temperature, and strength of the magnetic field meeting the conditions of the applicability of QCR theory is derived and investigated. It is demonstrated that the appearance of tripler MI states of an electron with an isotropic effective mass in a strong magnetic field determines the QCR line half-width delta omega(T,H) as a function of temperature and field in the case when scattering is due to small-size neutral donors. The developed approach eliminates considerable discrepancies between predictions of QCR theory and the results of QCR experiments (in semiconductors with an isotropic spectrum of carriers scattered by neutral impurities) that employ FIR lasers with discharge (H2O and D2O lasers, 220-119 mu m) and optical (HCOOH and CH3OD lasers, 513-295 mu m) pumping as sources of electromagnetic waves. For carriers with a sharply anisotropic effective mass, we revealed and investigated oscillations of the half-width of the absorption QCR line. These oscillations are periodic in the magnetic field H with a period corresponding to H-1/4. The mechanism behind the revealed oscillations is associated with transitions from bound MI states of an electron in the presence of neutral centers to the continuum with a decrease in the strength of the magnetic field.

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Magnetic-impurity states of a particle with an anisotropic effective mass in a short-range potential

Andreev, AS; Andreev, SP; Gurvich, YA

LASER PHYSICS; vol. 7; issue 4; pp. 976-983; year: 1997

Abstract: Magnetic-impurity states of a particle with an anisotropic effective mass in the presence of an attractive potential of a center with a small radius r(c) much less than l = root c (h) over bar/eH (l is the magnetic length and H is the strength of the magnetic field) and an arbitrary depth are investigated. The possibility of the experimental detection of such states with the use of FIR-lasers is discussed.

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Does the Unruh effect exist? (vol 65, pg 902, 1997)

Belinskii, VA; Karnakov, BM; Mur, VD; Narozhnyi, NB

JETP LETTERS; vol. 66; issue 10; pp. 704-704; year: 1997

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Does the Unruh effect exist?

Belinskii, VA; Karnakov, BM; Mur, VD; Narozhnyi, NB

JETP LETTERS; vol. 65; issue 12; pp. 902-908; year: 1997

Abstract: It is shown that quantization on the Fulling modes presupposes that the field vanishes on the spatial boundaries of the Rindler manifold. For this reason, Rindler space is physically unrelated with Minkowski space and the state of a Rindler observer cannot be described by the equilibrium density matrix with the Fulling-Unruh temperature. Therefore it is pointless to talk about an Unruh effect. The question of the behavior of an accelerated detector in the physical formulation of the problem remains open. (C) 1997 American Institute of Physics.

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Ponderomotive forces and stimulated Compton scattering of free electrons in a laser field

Fedorov, MV; Goreslavsky, SP; Letokhov, VS

PHYSICAL REVIEW E; vol. 55; issue 1; pp. 1015-1027; year: 1997

Abstract: The relationship between ponderomotive forces and stimulated Compton scattering is investigated. It is shown that an electron interacting with a coherent classical light field experiences an action of both ponderomotive forces and forces arising from the stimulated Compton scattering. Both of these forces are shown to be expressed in terms of a single function interpreted as the ponderomotive potential. Ponderomotive forces are shown to exist only if both electron and light states have at least some degree of coherence they disappear if either the electron wave function is a pure plane wave or the field state is a pure quantum-electrodynamical state with definite numbers of photons (a pure Fock state). Stimulated Compton scattering is shown to depend also on the degree of coherence of the light field and of the free-electron wave function. Specific calculations are carried out for the plane-focused stationary Gaussian beam and for the stationary evanescent wave. Critical fields are found at which ponderomotive forces and forces arising due to the stimulated Compton scattering become of the same order of magnitude.

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Photoelectron velocity distribution at the time of ionization by elliptically polarized laser field

Goreslavsky, SP; Popruzhenko, SV

LASER PHYSICS; vol. 7; issue 3; pp. 700-705; year: 1997

Abstract: We show how the distribution in velocities at the moment of ionization by a strong low-frequency laser field could be introduced from quantum mechanical calculations and derive the one explicitly for the field with arbitrary elliptical polarization.

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Characteristic electron thermalization time in dielectric media

Ivliev, SV; Lyapidevskii, VK; Ryazanov, MI

TECHNICAL PHYSICS; vol. 42; issue 6; pp. 624-627; year: 1997

Abstract: An approximate solution is obtained far the thermalization transport equation for electrons with an energy below the atom ionization potential. The results are used to estimate the thermalization time and the time of removal of the ionization electron from its atom in the gaseous and liquid states of inert gases. (C) 1997 American Institute of Physics.

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Contribution to the theory of Lorentzian ionization

Karnakov, BM; Mur, VD; Popov, VS

JETP LETTERS; vol. 65; issue 5; pp. 405-411; year: 1997

Abstract: The probability w(L) of Lorentzian ionization, which arises when an atom or ion moves in a constant magnetic field, is calculated in the quasiclassical approximation. The nonrelativistic (upsilon less than or similar to e(2)/(h) over bar = 1, upsilon is the velocity of the atom) and ultrarelativistic (upsilon --> c = 137) cases are examined and the stabilization factor S, which takes account of the effect of the magnetic field on tunneling of an electron, is found. (C) 1997 American Institute of Physics.

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Energy distributions of particles transmitted through free foils at oblique incidence

Koborov, NN; Kuzovlev, AI; Kurnaev, VA; Remizovich, VS; Trifonov, NN

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SEC ON B-BEAM INTERAC ONS WITH MATERIALS AND ATOMS; vol. 129; issue 1; pp. 5-10; year: 1997

Abstract: Energy loss distributions of particles transmitted through free mylar foil of 25 mu g/cm(2) thickness for 10-25 keV protons incident at angles 0 less than or equal to theta(0) less than or equal to 60 degrees are measured. An analytical treatment is made using the Fokker-Planck approximation for the kinetic equation. Different factors that can affect energy loss distributions were taken into account: energy straggling during inelastic collisions, path length fluctuations due to multiple eleastic collisions and foil thickness fluctuations. A simple formula for the energy spectra FWHM is derived comprising all aforesaid factors. It is shown that the dependence of FWHM on these factors as function of theta(0) is different. So possible contribution of each factor can be evaluated from angle measurements of FWHM. Comparison of the analytical result with the experiment as well as computer simulations using TRIM-like code shows that the main contribution to measured FWHM is due to fluctuations of the inelastic energy losses.

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Relative contribution of various factors to the formation of the energy spectrum of fast, medium-energy, charged particles and ions transmitted through a thin target with fluctuations of the target thickness

Koborov, NN; Kuzovlev, AI; Kurnaev, VA; Remizovich, VS

TECHNICAL PHYSICS; vol. 42; issue 5; pp. 529-541; year: 1997

Abstract: The characteristics of the energy spectra of kiloelectron-volt protons transmitted through a freestanding foil are investigated theoretically and experimentally as functions of the angle of incidence of the beam on the target. Analytical expressions for the average characteristics of the transmitted-particle energy spectrum are determined for the case of small-angle scattering. The combined influence of various factors affecting the formation of the energy spectra is taken into account: systematic stopping of particles in the medium, fluctuations of the particle energy losses in inelastic collisions, bending of the particle trajectories due to multiple elastic scattering, and fluctuations of the target thickness. It is shown that the contributions of these factors to the width of the transmitted-particle energy spectrum depend differently on the angle of incidence of the beam on the target surface. On the basis of this differentiation it is inferred from the experimental dependence of the width of the energy spectra of kiloelectron-volt protons transmitted through a free-standing foil on the angle of incidence of the beam that fluctuations of the particle energy losses in inelastic collisions are the predominant factor in the formation of the proton energy spectra. (C) 1997 American Institute of Physics. [S1063-7842(97)01305-6].

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Propagation of a stationary light flux in a randomly inhomogeneous 3D medium with a six-directional scattering phase function

Marinyuk, VV; Tishin, IV; Remizovich, VS

LASER PHYSICS; vol. 7; issue 2; pp. 461-465; year: 1997

Abstract: In this paper, we study the propagation of light fluxes in a semi infinite randomly inhomogeneous absorbing medium with chaotically distributed scattering centers. The real law of single scattering is simulated with a six-directional model scattering phase function. The case of normal incidence of a broad stationary light flux on a flat surface of a medium is considered. With such a geometry of the problem, we can derive the exact analytical solution to the transfer equation with the six-directional scattering phase function specified above. The problem of reflection of light is analyzed in detail. The total coefficient of reflection from such a model medium is calculated. The results of our analysis are compared with the exact reflection coefficient corresponding to an isotropic law of single scattering described by the Chandrasekhar formula. It is shown that the mean value of the reflection coefficient calculated with the use of six- and two-directional scattering phase functions coincides with predictions of the Chandrasekhar formula within an accuracy of 5% in a broad range of the values of the absorption coefficient of a medium.

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The imaginary-time method for relativistic problems

Popov, VS; Mur, VD; Karnakov, BM

JETP LETTERS; vol. 66; issue 4; pp. 229-235; year: 1997

Abstract: A relativistic version of the imaginary-time method is presented. The method is used to calculate the probability w of ionization of a bound state by electric and magnetic fields of various configurations (including the case when the binding energy E-b is comparable to mc(2)). The formulas cover as limiting cases both the ionization of nonrelativistic bound systems (atoms and ions) and the case E-b=2mC(2), when w equals the probability of electron-positron pair production from the vacuum in the presence of a strong field. (C) 1997 American Institute of Physics.

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Quasiclassical theory of atomic ionization in electric and magnetic fields

Popov, VS; Karnakov, BM; Mur, VD

PHYSICS LETTERS A; vol. 229; issue 5; pp. 306-312; year: 1997

Abstract: Using the ''imaginary time'' method we have calculated (in the quasiclassical approximation) the probability of ionization of the atomic s-state in static electric and magnetic fields. The Coulomb interaction between the emitted electron and the atomic remainder is taken into account. The results obtained are valid for external fields E and H which are smaller than characteristic atomic fields. The case of mutually orthogonal fields (the Lorentz ionization) is carefully studied. (C) 1997 Elsevier Science B.V.

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Application of the method of the separation of fluxes to the reflection of light: Calculation of the partial reflection function for a linear scattering phase function

Remizovich, VS; Radkevich, AV

LASER PHYSICS; vol. 7; issue 4; pp. 952-966; year: 1997

Abstract: In this paper, we continue the investigation of the reflection of light from a semi-infinite medium. For a medium with a Linear scattering phase function, we use the method of separation of fluxes to calculate analytically the first partial reflection function (FPRF) S-(1) in the case of the normal incidence of radiation upon a surface of a medium. The FPRF is compared with the exact reflection function (RF) calculated using the Ambartsumyan formulas. In the case of the oblique incidence of radiation upon a surface of a medium, we also calculate the FPRF integrated over the azimuth and compare the obtained results with the predictions of the Ambartsumyan theory. We analyze the influence of the single-scattering anisotropy on the accuracy of the S-(1)-approximation. It is demonstrated that the FPRF describes the main features of the spectrum of reflected radiation, and the remaining reflected radiation, formed by photons that change the sign of their velocity projection c(z) on the z-axis three and more times, is described by a dependence close to a cosine function.

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Application of the method of separated fluxes and the Ambartsumyan invariance principle in albedo problems of the linear theory of radiation transfer in disordered media

Remizovich, VS; Tishin, IV

LASER PHYSICS; vol. 7; issue 4; pp. 1014-1020; year: 1997

Abstract: In this paper, we use a nonconventional approach that combines the method of separated fluxes and the Ambartsumyan invariance principle to calculate the function of reflection of photons from a semi-infinite homogeneous medium with chaotically distributed scattering centers. The method of separated fluxes allows us to present the total reflection function (RF) as a sum of partial RFs. Each of the partial RFs describes a part of reflected radiation consisting of photons that change the sign of their velocity projection on the direction of the interior normal to the surface of a scattering medium a definite (odd) number of times (1, 3, 5, etc.). Using the nonlinear Ambartsumyan equation for the total RF, we derive a set of linear integral equations for all partial RFs. In particular, we show that the equation for the first partial RF can be derived from the Ambartsumyan equation if we discard the nonlinear term in this equation. Importantly, all the derived equations are of the same type and differ from each other only by inhomogeneous terms. This circumstance permits us to use the method of Green's functions for the solution of these equations.

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Angular intensity correlations in reflection of light from a random medium

Rogozkin, DB

PHYSICS LETTERS A; vol. 236; issue 1-2; pp. 159-166; year: 1997

Abstract: The correlation of the angular reflection coefficients and their whole distribution function are studied. The intensity fluctuations for different directions are shown to be negatively correlated. A deviation of the distribution function from the Rayleigh law indicates that large fluctuations of the reflected intensity are suppressed. All these peculiarities result from the constraints imposed by conservation of the energy flux. (C) 1997 Elsevier Science B.V.

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Long-range intensity correlations for the multiple scattering of waves in unordered media

Rogozkin, DB

JOURNAL OF EXPERIMENTAL AND THEORE CAL PHYSICS; vol. 84; issue 5; pp. 916-939; year: 1997

Abstract: The long-range correlations in the reflected and transmitted fluxes in the case of the coherent transport of waves in an unordered medium with discrete inhomogeneities are considered. The correlator and spectrum of the intensity fluctuations are expressed in a general form in terms of the one-center scattering amplitude and the propagators of the mean radiated intensity, The random interference of the waves and the fluctuations of the number of scattering centers in a microvolume of the medium are taken into account simultaneously. Detailed calculations are performed for two limiting radiation propagation regimes, viz., spatial diffusion and small-angle multiple scattering. It is shown that the conservation of the total flux upon elastic scattering leads to the formation of a dip in the spectrum and, accordingly, a negative correlation between the intensities at large distances. In the case of spatial diffusion this feature is displayed upon reflection, and in the case of small-angle multiple scattering it is displayed upon transmission through a slab. The relative roles of the various sources of intensity fluctuations, as well as the sensitivity of the correlations to factors that influence the wave propagation regime, viz., the finite size of the scattering sample, absorption in the medium, and the presence of a frequency shift in the incident waves, are analyzed. We find that fluctuations in the distribution of the scatterers show up mast strongly in a medium with strong, i.e., ''non-Born,'' centers, especially if they exhibit absorption. (C) 1997 American Institute of Physics.

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On the possibility of the condensation of the charged rho-meson field in dense isospin asymmetric baryon matter

Voskresensky, DN

PHYSICS LETTERS B; vol. 392; issue 3-4; pp. 262-266; year: 1997

Abstract: It is shown that at sufficiently large density the isospin-asymmetric baryon matter may undergo the phase transition to the rho-condensate state being characterized by the finite values of the charged rho-meson mean fields. The appearance of such a condensate diminishes the asymmetry energy of the baryon matter. It is shown that in the neutron stars the corresponding phase transition is of the first order. Possible consequences are enumerated.

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Evaluation of the mean intensity of the P-odd mixing of nuclear compound states

Rodin, VA; Urin, MH

PHYSICAL REVIEW C; vol. 55; issue 3; pp. 1583-1586; year: 1997

Abstract: A temperature version of the shell-optical-model approach is given to describe the low-energy compound-to-compound transitions induced by external single-particle fields. The approach is applied to evaluate the mean intensity of the P-odd mixing of nuclear compound states. The unified description for the mixing and electromagnetic transitions allows one to evaluate the mean intensity without the use of free parameters. Calculation results are compared with available experimental data.

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Line broadening in a quantum cyclotron resonance due to neutral impurities

Andreev, AS; Andreev, SP; Gurvich, YA; Podlivaev, IF

LASER PHYSICS; vol. 6; issue 6; pp. 1214-1217; year: 1996

Abstract: We derive and analyze a formula that describes the absorption-line contour corresponding to a quantum cyclotron resonance (T much less than (h) over bar omega(H) and Delta omega much less than omega(H), where T is the temperature, omega(H) = eH/m*c is the cyclotron frequency, Delta omega = omega - omega(H) is the frequency detuning, m* is the effective mass, and omega is the frequency of the electric field), which occurs in the scattering of electrons from centers of a small radius r(c) (r(c)(2) much less than l(2) = c (h) over bar/eH, where H is the magnetic field). The derived formula is applicable for any Delta omega, T, and H that satisfy the above inequalities. Considerable discrepancies between theoretical predictions and the results of experiments on quantum cyclotron resonances in semiconductors with the use of FIR lasers are eliminated.

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On description of the direct nucleon decay of giant resonances

Chekomazov, GA; Muraviev, SE; Urin, MH

NUCLEAR PHYSICS A; vol. 599; issue 1-2; pp. C259-264; year: 1996

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An effect of diffusion on appearance of axisymmetric-form instability of new-phase islands

Devyatko, YN; Rogozhkin, SV; Fedotov, BA

METALLOFIZIKA I NOVEissueHIE TEKHNOLOGII; vol. 18; issue 3; pp. 29-34; year: 1996

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Theory of the kinetics of nucleation in adsorbing layer: The approach based on the relaxation of order parameter field

Devyatko, YN; Rogozhkin, SV; Fedotov, BA

SURFACE SCIENCE; vol. 345; issue 1-2; pp. 138-154; year: 1996

Abstract: We use a Ginzburg-Landau type equation for the order parameter field to study the growth kinetics of two-dimensional new phase nuclei, as well as the phenomenon of instability of the azimuthal form of growing nuclei. A connection between the developed approach and phenomenological Zeldovich-Volmer (ZV) theory is established. The onset of various types of conditions imposed in ZV theory on the nucleus boundary is considered. We obtain instability diagrams of the angular perturbations and show that the instability occurs when the main growth mechanism is a diffusive one. Also, we determine the parameters region where the criteria obtained in this paper are the same as the results of phenomenological ZV theory and the continuum DLA model. Additionally, we study the criteria for the growth of angular perturbations in the case of a nonquasistationary growth regime.

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Contribution of the local heating to sputtering processes in magnetics near the Curie temperature

Devyatko, YN; Makletsov, AA; Pivovarov, AN; Troyan, VI

IZVESTIYA AKADEMII NK SERIYA FIZICHESKAYA; vol. 60; issue 4; pp. 177-183; year: 1996

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The BSI model and relativistic ponderomotive scattering

Goreslavsky, SP

LASER PHYSICS; vol. 6; issue 1; pp. 74-78; year: 1996

Abstract: Longitudinal and transverse relativistic drifts that follow barrier-suppression ionization are calculated analytically for short and long laser pulses and both polarizations.

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Momentum distribution of photoelectrons in a strong low-frequency elliptically polarized laser field

Goreslavskii, SP; Popruzhenko, SV

LASER PHYSICS; vol. 6; issue 4; pp. 780-784; year: 1996

Abstract: The distribution of photoelectrons over momenta is derived in a closed form for the tunneling regime of ionization by an elliptically polarized laser field. It is demonstrated that, as the polarization changes from circular to linear, within a broad range of ellipticity, the angular distribution is stretched along the small axis of the polarization ellipse, in the direction transverse to the maximum electric field. Only when the ellipticity is rather small, the distribution is modified and becomes stretched along the electric field, as it should be in a linearly polarized field.

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Differential distribution of photoelectron in elliptically polarized high-power low-frequency laser field

Goreslavskii, SP; Popruzhenko, SV

ZHURNAL EKSPERIMENTALNOI I TEORETICHESKOI FIZIKI; vol. 110; issue 4; pp. 1200-1215; year: 1996

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Propagation of electromagnetic radiation through random media with long-range fluctuation correlations of the dielectric constant

Gorodnichev, EE; Kuzovlev, AI; Rogozkin, DB

LASER PHYSICS; vol. 6; issue 6; pp. 1188-1197; year: 1996

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Propagation of ions through the target at inclined incidence of the beam on the statistically homogeneous scatterer with nonuniform thickness

Koborov, NN; Kuzovlev, AI

IZVESTIYA AKADEMII NK SERIYA FIZICHESKAYA; vol. 60; issue 4; pp. 204-209; year: 1996

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The impact of kaon polarization in nuclear matter on the K- production in heavy-ion collisions

Kolomeitsev, EE; Voskresensky, DN; Kampfer, B

INTERNA ONAL JOURNAL OF MODERN PHYSICS E-NUCLEAR PHYSICS; vol. 5; issue 2; pp. 313-328; year: 1996

Abstract: The impact of the kaon polarization in nuclear matter on the K- yield in intermediate-energy heavy-ion collisions is investigated. Our scenario of the strange particle production and dynamics is based on an expanding fireball model. This allows for a proper account of in-medium effects. A relation between observed K+ and K- yields is derived. Differential K- cross-sections are calculated and compared with available experimental data taken at various collision energies. It turns out that in-medium effects can modify the K- yields by factors 2 to 5 at beam energies between 2 and 1 AGeV.

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Hot and dense pion gas with finite chemical potential

Kolomeitsev, EE; Voskresensky, DN; Kampfer, B

ACTA PHYSICA POLONICA B; vol. 27; issue 11; pp. 3263-3270; year: 1996

Abstract: A dense and hot pion system with a dynamically fixed particle number and an arbitrary charge is investigated with respect to ultra-relativistic heavy-ion collisions. The Lagrangian for describing such a system is derived from Weinberg's chiral Lagrangian for the pion-pion interaction. Pion polarization operators are calculated within the Hartree approximation. The pion spectrum in the isospin symmetrical gas is presented. The effective in-medium pion gap depends sensitively on the density and the temperature, and it is found to exceed both the free pion mass and the corresponding value for the pion gas in chemical equilibrium. The possibility of a Bose-Einstein condensation is also discussed.

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Low frequency surface acoustic waves propagating in a system of n anisotropic layers on an anisotropic substrate

Kosachev, VV; Shchegrov, AV; Vasiliev, IL; Yakovkin, IB

LID STATE COMMUNICA ONS; vol. 99; issue 2; pp. 105-108; year: 1996

Abstract: Propagation of surface acoustic waves in a system of n anisotropic layers on a semi-infinite anisotropic substrate is considered. In the limit when the wavelength is large compared to the total thickness of the layers, the dispersion relation for surface waves is derived. The dispersion relation agrees with the one-layer case and the case of isotropic media studied elsewhere. Possible applications of the results obtained are discussed.

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Contribution of the surface roughness of hexagonal crystal into the low temperature surface specific heat

Kosachev, VV; Brantov, AV

LID STATE COMMUNICA ONS; vol. 99; issue 11; pp. 783-787; year: 1996

Abstract: The effect of surface roughness on the low temperature surface specific heat of a hexagonal crystal is investigated in this paper by means of the Green's function method developed earlier, taking into account a considerable correction introduced into it. The surface whose contribution to the specific heat is being calculated is parallel on average to the basal plane of a hexagonal medium. An expression in analytical form is derived for the contribution of the weak roughness to the low temperature surface specific heat of a hexagonal medium which represents a correction to the result for the surface specific heat of a hexagonal crystal with a free flat boundary. In the limiting case of an isotropic medium the result coincides with that of earlier research. The analysis carried out proves that taking account of the surface roughness of a hexagonal crystal results on the whole in the increasing surface specific heat for roughness parameters corresponding to an optically smooth surface.

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Calculation of nonstationary light fields in a homogeneous 2D medium with a model four-directional scattering phase function under the normal incidence of radiation upon a medium surface

Marinyuk, VV; Remizovich, VS; Tishin, VS

LASER PHYSICS; vol. 6; issue 5; pp. 928-941; year: 1996

Abstract: In this paper, we consider the propagation of light fluxes in an absorbing medium with a model four-directional scattering phase function in the case of irradiation of matter by a delta-pulse light source. We investigate thoroughly the intensities of descending and ascending radiation at various depths as functions of time for an elementary two-directional scattering phase function. Thus, we give a detailed analysis of the problem of random nonstationary walk of photons in 2D and 3D media. The expressions for the descending and ascending fluxes are obtained in the form of series expansions in partial fluxes, i.e., in the number of changes in the sign of the velocity projection on the z-axis. Time dependence of the intensity of descending and ascending radiation at various depths in the case of a two-directional single-scattering law is analyzed. We focus special attention on the analysis of characteristics of reflected radiation in the most general case of a four-directional scattering phase function. In some particular cases, we give simple analytical expressions for the temporal dependence of the reflection coefficient.

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Coulomb corrections to nuclear scattering lengths and effective ranges for weakly bound systems

Mur, VD; Popov, VS; Sergeev, AV

PHYSICS OF ATOMIC NUCLEI; vol. 59; issue 1; pp. 62-71; year: 1996

Abstract: A procedure is considered for extracting the purely nuclear scattering length a(s) and effective range r(s) (which correspond to a strong-interaction potential V-s with disregarded Coulomb interaction) from the experimentally determined nuclear quantities a(cs) and r(cs), which are modified by Coulomb interaction. The Coulomb renormalization of a(s) and r(s) is especially strong if the system under study involves a level with energy close to zero (on the nuclear scale). This applies to formulas that determine the Coulomb renormalization of the low-energy parameters of s scattering (l=0). Detailed numerical calculations are performed for coefficients appearing in the equations that determine Coulomb corrections for various models of the potential V-s(r). This makes it possible to draw qualitative conclusions about the dependence of Coulomb corrections on the form of the strong-interaction potential and, in particular, on its small-distance behavior. A considerable enhancement of Coulomb corrections to the effective range r(s) is found for potentials with a barrier.

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Coulomb corrections to scattering lengths and effective ranges for l not equal 0

Mur, VD; Popov, VS; Sergeev, AV

PHYSICS OF ATOMIC NUCLEI; vol. 59; issue 11; pp. 1888-1894; year: 1996

Abstract: Coulomb corrections to the low-energy scattering parameters (scattering lengths and effective ranges) of states with nonzero orbital angular momentum are studied. The greatest attention is paid to the case of the p wave. Resonance scattering is considered for a system with a shallow nuclear bound or quasistationary (resonance) p level. Coulomb corrections are calculated numerically, and their dependence on the shape of the strong-interaction potential-in particular, on its short-distance behavior-is studied in detail.

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1/n-expansion for asymptotic coefficients of radial wave functions in quantum mechanics

Popov, VS; Karnakov, BM; Mur, VD

PHYSICS LETTERS A; vol. 224; issue 1-2; pp. 15-21; year: 1996

Abstract: Using the 1/n-expansion, we obtain analytic formulae for the bound state radial wave functions, including its asymptotic coefficients at r --> 0 and r --> infinity, for an arbitrary smooth potential V(r). The formulae are asymptotically exact in the limit n( )r--> infinity (n = n(r) + l + 1 is the principal quantum number and the expansion parameter is 1/n). Comparison with exact solutions and numerical calculations for the power-law and short-range potentials show that the applicability region of these formulae is usually prolonged up to small quantum numbers, n similar to 1. With growing n(r), the accuracy of the formulae decreases, but the WKB method becomes applicable in this case.

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A model-independent description of dt and d(3)He systems near low-energy resonances

Popov, VS; Karnakov, BM; Mur, VD

HYPERFINE INTERAC ONS; vol. 102; pp. 401-411; year: 1996

Abstract: The effective range expansion is used to obtain a model-independent description of dt and d(3)He systems in the vicinity of the low-energy resonances He-5*(3/2(+)) and Li-5* (3/2(+)). The Coulomb-modified nuclear scattering lengths a(cs) and effective ranges r(cs) with angular momentum l = 0 as well as the astrophysical function s(E) are calculated from the modern experimental data for cross sections of the dt --> na and d(3)He --> p alpha per fusion reactions in the vicinity of the resonances. To this end the generalization of the Smorodinsky formula for effective range to the case of potentials with the Coulomb barrier, as well as the phase analysis of the elastic n alpha-scattering near the resonance He-5* (3/2(+)), are essentially used. The analytical structure of the scattering amplitudes in presence of absorption in the system is studied. Two series of the Coulomb poles of the dt-scattering amplitude in the complex k-plane, condensing to the elastic threshold, are found.

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On matching conditions in the WKB method

Popov, VS; Karnakov, BM; Mur, VD

PHYSICS LETTERS A; vol. 210; issue 6; pp. 402-408; year: 1996

Abstract: The modified matching conditions for quasiclassical wave functions on both sides of a turning point for the radial Schrodinger equation have been obtained. They differ significantly from the usual Kramers condition which holds for the one-dimensional case. Namely, the ratio C-2/C-1 in the subbarrier and the classical allowed regions is not a universal constant (C-2/C-1 = 1/2, as usual), but depends on the values of the orbital angular momentum I, energy E and on the behaviour of the potential V(r) at r --> 0. The comparison with exact and numerical solutions of the Schrodinger equation shows that the modified matching conditions not only make the quasiclassical approximation in the subbarrier region asymptotically exact within the n --> infinity limit, but also considerably enhances its accuracy even in the case of small quantum numbers, n similar to 1. The power-law, funnel and short-range potentials are considered in detail.

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Model-independent description of dt-system and d(3)He-system in the vicinity of low-energy resonances

Popov, VS; Karnakov, BM; Mur, VD

ZHURNAL EKSPERIMENTALNOI I TEORETICHESKOI FIZIKI; vol. 110; issue 5; pp. 1537-1556; year: 1996

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Application of the method of separated fluxes for analytical calculations of angular and energy spectra of ions passing through amorphous solids

Radkevich, AV; Remizovich, VS

IZVESTIYA AKADEMII NK SERIYA FIZICHESKAYA; vol. 60; issue 4; pp. 195-203; year: 1996

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Analysis of the structure of light fields in disordered media with model bidirectional phase functions using the method of separation of fluxes

Remizovich, VS; Radkevich, AV

LASER PHYSICS; vol. 6; issue 1; pp. 1-9; year: 1996

Abstract: In this paper, we use the method of separation of fluxes to analyze Light fields in the case of the normal incidence of a stationary laser beam upon the surface of a semi-infinite medium with disordered scattering centers described by the model bidirectional phase function. The structure of ascending and descending fluxes is thoroughly investigated. Conditions are found when only one partial flux dominates in descending and ascending radiation. The dependence of the total and partial coefficients of reflection from a semi-infinite medium on the main optical characteristics of the medium is analyzed. Conditions are determined when the calculation of the total reflection coefficient can be replaced by the calculation of the first partial reflection coefficient.

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Reflection of a light flux from a randomly inhomogeneous 2D medium with a model four-directional scattering phase function under the oblique incidence of radiation upon a surface

Remizovich, VS; Marinyuk, VV; Tishin, IV

LASER PHYSICS; vol. 6; issue 2; pp. 394-400; year: 1996

Abstract: In this paper, we use the classical Boltzmann transfer equation to analytically calculate the intensity of radiation at various depths under the oblique incidence of a stationary light flux upon a surface of a semi-infinite random 2D medium with a model four-directional scattering phase function of separate filamentary scatterers. Analysis of the dependence of the total light reflection coefficient on the basic optical characteristics of a medium and on the incidence angle theta(0) of radiation upon a medium surface is performed. In particular, the dependence of the total reflection coefficient on the incidence angle and the probability of the photon survival in the case of isotropic 2D scattering from a separate center is studied. The results obtained are compared with the exact solutions for an isotropically scattering 2D medium.

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Calculation of light fields using the modified 2P(0) approximation in the framework of the method of separation of light fluxes

Remizovich, VS; Radkevich, AV

LASER PHYSICS; vol. 6; issue 4; pp. 679-694; year: 1996

Abstract: In this paper, we consider the problem of propagation of optical radiation under conditions of flat geometry of the scattering medium. An original approach to the calculation of light fields based on the method of separation of fluxes with subsequent expansion of descending and ascending radiation in the modified Legendre polynomials is suggested. Of principal importance is the separation of the anisotropic part of radiation in the descending flux, which corresponds to photons that systematically propagate toward the inside of the medium. In the framework of the modified 2P(0) approximation for the light fluxes, the set of equations is formulated. It is shown that the value of the mean single-scattering angle is the major characteristic of a medium directly connected with the probability of a change in the sign of the photon velocity projection on an arbitrary direction. The Green's function of the set of equations in the modified 2P(0) approximation for a flat scatterer of finite thickness is determined. In a particular case of isotropic single scattering, the expression for the reflection coefficient from a semi-infinite medium is obtained. Comparison of obtained results with the results of calculations in the two-flux approximation and with the exact results of Ambartsumyan and Chandrasekhar is presented.

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Application of the method of the separation of fluxes to the reflection of light: Calculation of the partial reflection function

Remizovich, VS; Radkevich, AV

LASER PHYSICS; vol. 6; issue 6; pp. 1180-1187; year: 1996

Abstract: In this paper, we continue the investigation of the propagation of radiation in absorbing media using the method of the separation of fluxes. A regular procedure for the calculation of the Green's function is described in the case when the expansion of the scattering phase function in Legendre polynomials involves a finite number of terms. The Green's functions for the isotropic and linear scattering laws are calculated. The partial reflection function and the partial reflection coefficient in an isotropically scattering medium that describe the contribution of those photons in reflected radiation that change the sign of their velocity projection on the z-axis exactly once are analytically calculated. It is shown that the remaining part of reflected radiation, which involves photons that change the sign of their velocity projection on the z-axis three or more times, obeys the well-known cosine law. The results obtained for the partial reflection function and the partial reflection coefficient are compared with the results of calculation using the Chandrasekhar formulas.

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Long-range intensity correlations in a disordered medium

Rogozkin, DB; Cherkasov, MY

PHYSICS LETTERS A; vol. 214; issue 5-6; pp. 292-300; year: 1996

Abstract: We present rigorous calculations for the long-range intensity correlations in multiple wave scattering from a disordered medium. General relations are derived beyond the Born approximation for both the scattering amplitude and the Hikami vertex. The correlations between reflection and transmission coefficients are analyzed for a thick slab within the framework of the diffusion approximation. Besides the coherent contribution to the correlation function, the incoherent one is considered in detail. Conditions are discussed under which the incoherent contribution becomes particularly prominent.

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Approximate symmetries in nuclei and 2 nu beta beta-decay rate

Rumyantsev, OA; Urin, MH

IZVESTIYA AKADEMII NK SERIYA FIZICHESKAYA; vol. 60; issue 11; pp. 18-29; year: 1996

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Nonlinear waves in metals

Skobov, VG; Chernov, AS

ZHURNAL EKSPERIMENTALNOI I TEORETICHESKOI FIZIKI; vol. 109; issue 3; pp. 992-1005; year: 1996

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Where can we look for possible manifestations of kaon condensation in heavy-ion collisions?

Voskresensky, DN

PHYSICS OF ATOMIC NUCLEI; vol. 59; issue 5; pp. 811-815; year: 1996

Abstract: The possibility of observing manifestations of <K+K-K0(K)(0)over bar> condensates in peripheral heavy-ion collisions for energies E(lab) > E(c) similar to 1 GeV/A is discussed. The condensates can be observed via pronounced peaks in kaon and Lambda radiation at zero angle, provided that the momenta in the projectile and spectator frames are k(parallel to)(E(lab)) greater than or equal to 3m(pi) for K+K0 and k(parallel to)(E(lab))greater than or equal to 8m(pi) for <K-(K-0)over bar>.

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Kinetic description of a pion gas in ultrarelativistic collisions of nuclei: Turbulence and bose condensation

Voskresensky, DN

PHYSICS OF ATOMIC NUCLEI; vol. 59; issue 11; pp. 2015-2023; year: 1996

Abstract: The kinetics of a pionic fireball that arises in ultrarelativistic collisions of nuclei is studied. Analysis is performed in a simplified model employing pions of only one type that interact via the Hamiltonian H'=g/phi/(4)/4. A kinetic equation is formulated for pionic quasiparticles. Relaxation of strongly nonequilibrium initial distributions is discussed. For the initial distributions, the parameter values are chosen in such a way that the system under study relaxes to a distribution that has a form close to that of experimental distributions and which is characterized by a sharp growth at low momenta. These parameters correspond to the possibility that Bose condensation occurs as the pionic system under study evolves. The evolution of pion distributions at low momenta is analyzed. It is shown that, after a lapse of time, the system goes over to a turbulent regime as the energy of pions decreases. At still lower energies, the distribution becomes self-similar. The time after which a Bose condensate arises is determined. A possible scenario of pionic-fireball evolution is proposed on the basis of the results obtained in this study.

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Classical and quantum many-body description of bremsstrahlung in dense matter - Landau-Pomeranchuk-Migdal effect

Knoll, J; Voskresensky, DN

ANNALS OF PHYSICS; vol. 249; issue 2; pp. 532-581; year: 1996

Abstract: Some considerations about the importance of coherence effects for bremsstrahlung processes in nonequilibrium dense matter (Landau-Pomeranchuk-Migdal effect) are presented. They are of particular relevance for the application to photon and di-lepton production from high energy nuclear collisions, to gluon radiation in QCD transport, or parton kinetics and to neutrino and axion radiation From supernova explosion and from hot neutron stars. The soft behavior of the bremsstrahlung from a source described by classical transport models is discussed and pocket correction formulas for the in-matter radiation cross sections are suggested in terms of standard transport coefficients. The radiation rates are also discussed within a nonequilibrium quantum field theory (Schwinger-Kadanoff-Baym-Keldysh) formulation. A classification of diagrams and corresponding resummation in physically meaningful terms is proposed, which considers the finite damping width of all source particles in matter. This way each diagram in this expansion is already Gee from infra-red divergences. Both, the correct quasi-particle and quasi-classical limits are recovered from this subset of graphs. Explicit results are given for dense matter in thermal equilibrium. The diagrammatic description may suggest a formulation of a transport theory that includes the propagation of off-shell particles in nonequilibrium dense matter. (C) 1996 Academic Press, Inc.

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ON DIRECT NUCLEON DECAY OF THE GIANT-DIPOLE RENANCE AND PHOTONUCLEON REAC ONS

CHEKOMAZOV, GA; URIN, MH

PHYSICS LETTERS B; vol. 354; issue 1-2; pp. 7-13; year: 1995

Abstract: A semimicroscopical approach is proposed to describe the partial cross sections of the photonucleon reactions proceeding via the giant dipole resonance and the branching ratios for the direct nucleon decay of this resonance. The approach is formulated in two steps. The first (microscopical) one consists in the use of the continuum-RPA for calculating the energy, partial nucleon and radiative widths of those 1(-) collective particle-hole states (doorway states), which exhaust most of the classical sum rule. The second step concerns the coupling of the doorway state to complex configurations. It is phenomenologically taken into consideration with the use of a statistical assumption. Applications of the approach are given.

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NONLINEAR NONLOCAL WAVE IN METALS

CHERNOV, AS; SKOBOV, VG

PHYSICS LETTERS A; vol. 205; issue 1; pp. 81-84; year: 1995

Abstract: It is shown that the decrease of the collisionless absorption in the magnetic-field region below the helicon absorption edge might be so considerable in the nonlinear regime that propagation of a new rf wave becomes possible. The wave frequency is proportional to the fourth power of its wave number, and its damping is inversely proportional to the carrier mean free path. The wave is excited most effectively at magnetic-field values much lower than the helicon threshold. Conditions necessary for observing the wave are presented.

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GIANT QUANTUM OSCILLA ONS OF CYCLOTRON Abstract:RP ON IN METALS

CHERNOV, AS; SKOBOV, VG

PHYSICS LETTERS A; vol. 199; issue 3-4; pp. 245-248; year: 1995

Abstract: It is shown that quantization of electron energy levels in a strong magnetic field H can give rise to giant oscillations of cyclotron absorption of a radio wave in a metal as a function of H.

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Ponderomotive scattering at relativistic laser intensities

Goreslavsky, SP; Narozhny, NB

JOURNAL OF NONLINEAR OP CAL PHYSICS & MATERIALS; vol. 4; issue 4; pp. 799-815; year: 1995

Abstract: We present a summary on the exact solutions to the classical relativistic equations of motion in the held of a plane electromagnetic wave and describe a modification of the averaging procedure, which yields equations governing the average electron motion in the field of a focused laser pulse when an electron oscillates at relativistic velocity. Applications to the barrier suppression ionization and Thompson radiation are briefly discussed.

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RELA Vissue C DRIFT OF AN ELECTRON UNDER THE INFLUENCE OF A SHORT INTENSE LASER-PULSE

GORESLAVSKY, SP; FEDOROV, MV; KILPIO, AA

LASER PHYSICS; vol. 5; issue 5; pp. 1020-1028; year: 1995

Abstract: In the context of the problem of ionization of an atom by a very strong laser field, we use the planewave approximation to consider a drift of a classical electron in a light field. The conditions of applicability of the employed approximations are discussed. In particular, the conditions for neglecting spatial inhomogeneity of the field and electron drift due to gradient forces are analyzed. We present the solutions to relativistic equations of motion expressed in terms of the integral of the electric-field strength in the incident wave over the phase. We discuss competition, similarity, and distinguishing features of the electron drift along the direction of the electric-field vector (drift due to initial conditions) and along the direction of wave propagation (drift due to the Lorentz force). The applicability of the adiabatic approximation for the analytical calculation of the integrals that determine solutions is analyzed.

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SMALL-ANGLE MUL PLE LIGHT-SCATTERING IN RANDOM-HETEROGENEOUS MEDIA

GORODNICHEV, EE; ROGOZKIN, DB

ZHURNAL EKSPERIMENTALNOI I TEORETICHESKOI FIZIKI; vol. 107; issue 1; pp. 209-235; year: 1995

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CONDI ONS OF JOINING IN THE BKB TECHNIQUE

KARNAKOV, BM; MUR, VD; POPOV, VS

ZHURNAL EKSPERIMENTALNOI I TEORETICHESKOI FIZIKI; vol. 107; issue 6; pp. 1768-1779; year: 1995

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Calculation of wave functions in the subbarrier region using 1/n expansion

Karnakov, BM; Pozdnyakov, SG

PHYSICS OF ATOMIC NUCLEI; vol. 58; issue 12; pp. 2088-2095; year: 1995

Abstract: A method is developed for calculating wave functions in the subbarrier region on the basis 1/n expansion. This method is used to calculate the asymptotic coefficient c(lp) at the origin. To illustrate the accuracy of the method the results are compared with results of numerical calculations for power-law potentials, short-range Yukawa potentials, and exponential potentials. Calculations ar performed for node-free states and for states with radial quantum number p = 1. The calculated correction of order 1/n is shown to considerably increase the accuracy of 1/n expansion, especially for p = 1 states (at n similar to 1, a zero-order approximation for such states is only an estimate).

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KAON POLARIZA ON IN NUCLEAR-MATTER

KOLOMEITSEV, EE; VOSKRESENSKY, DN; KAMPFER, B

NUCLEAR PHYSICS A; vol. 588; issue 4; pp. 889-917; year: 1995

Abstract: The kaon-nucleon interaction in nuclear matter is considered by taking into account tree graphs, p-wave interaction, pionic intermediate states, kaon fluctuations and some residual interaction. The latter one is constrained by Adler's consistency condition. The K-, K+, K-0, (K) over bar(0) polarization operators are calculated in cold nuclear matter with arbitrary isotopic composition. An extra s-wave repulsion is found, which probably shifts the critical point of a K- condensation with vanishing kaon momentum to large nucleon densities. Oppositely, an extra p-wave attraction is obtained, which may lead to a K- condensation at vanishing temperatures and densities rho greater than or equal to rho(c)(-) similar to(4-6)rho(0). The spectrum of the kaonic excitations in nuclear matter is analyzed and a new low-lying branch in the K- (and also (K) over bar(0)) spectrum is found. Its presence may lead to interesting observable consequences, such as the enhancement of the K- yields in heavy-ion reactions. At rho greater than or equal to rho(c)(-) the frequency of this low-lying branch becomes negative at non-vanishing momentum; that signals the onset of a new type inhomogeneous K- condensation. The K- condensate energy is calculated in the approximation of a small KK coupling constant. Accordingly, neutron star matter may undergo a first-order phase transition to proton matter with K- condensate at rho > rho(c)(-) due to p-wave interaction. The temperature dependence of the most important terms of the K- polarization operator is discussed. In a rather wide temperature region 0 < T < 1/2m(pi) a growing temperature enlarges the K-N attraction and promotes the kaon condensation. The possibility of p-wave (K) over bar(0) condensation is also considered. The question is qualitatively discussed whether proton matter with K- condensate or neutron matter with (K) over bar(0) condensate is energetically more favorable.

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Bose-Einstein condensation of pions in ultrarelativistic nucleus-nucleus collisions and the spectra of kaons

Kolomeitsev, EE; Voskresensky, DN

PHYSICS OF ATOMIC NUCLEI; vol. 58; issue 12; pp. 2082-2087; year: 1995

Abstract: The properties of a pion gas that is formed in ultrarelativistic collisions of nuclei are studied in the Weinberg model for pi pi interaction. The possible Bose-Einstein condensation of a dense pi(-) gas is considered. The Green's function and the spectrum of the overcondensate excitations are calculated. For a weak condensate, the results coincide with those obtained in [1] in the lambda phi(4) model (lambda = const), while for a developed condensate there are significant differences. The properties of kaons are considered for temperatures below the critical temperature for Bose-Einstein pion condensation. It is shown that, in the presence of a condensate, the K- effective mass becomes substantially larger, while the K+ effective mass becomes smaller. These features may manifest themselves in the observable momentum distributions of kaons.

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DissuePERSION AND ATTENUA ON OF SURFACE ACOUS C-WAVES OF VARIOUS POLARIZA ONS ON A STRESS-FREE RANDOMLY ROUGH-SURFACE OF LID

KOSACHEV, VV; SHCHEGROV, AV

ANNALS OF PHYSICS; vol. 240; issue 2; pp. 225-265; year: 1995

Abstract: An approach to obtaining the dispersion equation of surface acoustic waves (SAWs) on a stress-free, randomly rough surface of an anisotropic elastic medium is suggested. The problem is solved in the approximation of a weakly rough surface using Green's function technique. The dispersion and attenuation of sagittally and shear horizontally (SH) polarized SAWs are investigated both analytically and numerically for a three-dimensionally (3D) and a two-dimensionally (2D) rough surface of an isotropic medium. The results for 2D roughness are shown to be contained in the more general expressions for the 3D case, and the connection between the results for the 3D and the 2D cases is pointed out. Dispersion relations are derived for SAWs of both polarizations propagating in an arbitrary direction along a 2D rough surface. The SAW attenuation mechanisms are investigated at various incidence angles. It is concluded that all three mechanisms (viz. scattering into bulk transverse, longitudinal, and Rayleigh surface acoustic waves) are involved for the Rayleigh and SH polarized SAWs at certain incidence angles, whereas al the other angles only some of the mechanisms are. The criterion for the existence of SH polarized SAWs on a rough surface is considered. A possible increase of the SAW phase velocity on a rough surface compared with that for a flat boundary is discussed. In the limit lambda much greater than a (where a is the roughness correlation length) simple explicit expressions for the phase velocities of Rayleigh and SH polarized SAWs are derived. A comparison of the results obtained herein with those of other workers is presented. (C) 1995 Academic Press, Inc.

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DissuePERSION OF LOW-FREQUENCY SURFACE ACOUS C-WAVES OF DIFFERENT POLARIZA ON IN MUL LAYERED SYSTEMS

KOSACHEV, VV; SHCHEGROV, AV

LID STATE COMMUNICA ONS; vol. 93; issue 8; pp. 701-705; year: 1995

Abstract: Dispersion of surface acoustic waves (SAW) of sagittal and shear horizontal (SH) polarizations in a multilayered system of n isotropic layers on an isotropic substrate is investigated by the technique of effective boundary conditions in the framework of perturbation theory. The ratio of the total layer thickness to the wavelength of SAW is chosen to be small parameter. Under such assumptions the dispersion relations for the SAW of both sagittal and SH-polarizations are derived. The results for sagittally polarized SAW derived by means of perturbation theory are compared with numerical solution for a bilayered structure. Possible applications of the results obtained are discussed.

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PERTURBA ON-THEORY FOR QUASI-STA ONARY STATES

MUR, VD; POPOV, VS

PHYSICS OF ATOMIC NUCLEI; vol. 58; issue 8; pp. 1329-1341; year: 1995

Abstract: Perturbation theory (to the first order) for quasistationary states is developed in the semiclassical approximation. Formulas for the energy shift delta E, of a resonance, as well as for the variation of its width delta Gamma due to a perturbative potential delta U, are obtained. These formulas are valid both for subbarrier and above barrier resonances. The results are illustrated using a number of potentials for which semiclassical expressions can be compared with exact solutions of the Schrodinger equation. The proposed scheme is generalized to a multidimensional case with completely separating variables.

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WHERE TO LOOK FOR PION-CONDENSA ON IN HEAVY-ION COLLissueIONS

PIRNER, HJ; VOSKRESENSKY, DN

PHYSICS LETTERS B; vol. 343; issue 1-4; pp. 25-30; year: 1995

Abstract: The possibility to observe a pion condensate in peripheral nucleus - nucleus collisions at GSI energies is discussed. A condensate may be observed via pronounced peaks in pion production in a narrow region of momenta k(perpendicular to) similar or equal to (2-3) m(pi) corresponding to rather large rapidity values.

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APPLICA ON OF THE EIGENFUNC ONS METHOD AND AMBARTSUMYAN INVARIANCE-PRINCIPLE TO THE PROBLEM OF SMALL-ANGLE LIGHT-REFLEC ON FROM MEDIA WITH LARGE-SCALE SCATTERING CENTERS

REMIZOVICH, VS

LASER PHYSICS; vol. 5; issue 1; pp. 97-117; year: 1995

Abstract: The process of small-angle reflection of radiation under grazing incidence of a light beam upon a flat surface of a semi-infinite material layer with large-scale scattering centers is considered. The most important practical case is analyzed when the scattering phase function decreases with the increase of the single-scattering angle gamma slower than gamma(4), which precludes the use of the Fokker-Planck approximation for the description of light reflection. Two alternative approaches are considered: the ''invariant embedding'' method proposed by Ambartsumyan for small-angle light reflection and the method of eigenfunctions, which allows one to obtain a linear equation for the reflection function. Using the reflection function obtained in the framework of quasi-diffusion approximation with respect to photon scattering angles, the influence of the ratio of the angle of grazing incidence zeta(0) to the effective single-scattering angle gamma(ef) on the process of light reflection is investigated with the help of the Ambartsumyan equation. If zeta(0)/gamma(ef)(l) greater than or similar to 5, the quasi-diffusion approximation is shown to describe the process of backward scattering with high accuracy. Thorough analysis of the role of linear and nonlinear terms in the Ambartsumyan equation is made. It is shown that the nonlinear term in this equation can be neglected in the case of small-angle reflection.

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Method of separation of fluxes in the theory of light propagation in disordered media

Remizovich, VS

LASER PHYSICS; vol. 5; issue 4; pp. 751-786; year: 1995

Abstract: This paper considers the problem of determination of the light-field intensity in conditions of plane geometry of a scattering material layer. Discussing theoretically well-studied problems, namely, small-angle light reflection from media with sharply anisotropic scattering on separate centers, light reflection from a semiinfinite medium in conditions of isotropic scattering, P-1-approximation, and others, we demonstrate considerable difficulties connected with boundary conditions in the solution of different problems in the theory of optical radiation transfer. In order to overcome these difficulties, we propose an original method of separation of light fluxes. The essence of this method is in representing the intensities of both ascending and descending radiation as series. According to this method, instead of expanding the intensities in the multiplicity of collisions, we use expansions in the number of events that imply the sign reversal of the projection of the photon velocity on the direction normal to the boundaries of the scattering medium. We derive equations for independent calculation of ascending and descending radiation fluxes. Moreover, boundary conditions on material surfaces are exactly fulfilled for any approximate method of solving these equations. Taking a simple bidirectional scattering phase function as an example, we analytically calculate the ascending and descending radiation in a material layer with a finite thickness and partial fluxes of various multiplicities. We analytically calculated the Green's function in a medium with isotropic scattering and the Green's function that corresponds to the standard small-angle approximation in media with sharply anisotropic scattering. For the Henyey-Greenstein scattering law, we obtain a simple analytical expression for the intensity of transmitted radiation under oblique incidence of a light flux upon a material surface.

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Analytical calculation of stationary light fields in the propagation of laser radiation in randomly inhomogeneous 2D media with a model tetradirectional scattering phase function

Remizovich, VS; Marinyuk, VV; Tishin, IV

LASER PHYSICS; vol. 5; issue 6; pp. 1116-1125; year: 1995

Abstract: In this paper, we use the classical transfer equation to analytically calculate light fluxes in the case of the normal incidence of a stationary laser beam on the surface of a semi-infinite random 2D medium with a model tetradirectional scattering phase function of separate scattering centers. An algorithm for modeling real optical phase functions is thoroughly described. An appropriate modeling procedure is performed for the widespread Henyey-Greenstein phase function. We determine the law of spreading for a narrow laser beam with the depth and define the effective width of the reflected light flux. Asymptotic behavior of the radiation intensity is investigated in the longitudinal and transverse directions relative to the axis of the incident beam. We analyze the total coefficient of reflection of light from a semi-infinite medium irradiated by a broad stationary light flux as a function of the main optical characteristics of the medium. The exact solution of the problem is compared with the solution obtained with the use of the tetradirectional scattering phase function for isotropic scattering from an individual scattering center.

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EVALUA ON OF P-ODD MIXING MEAN INTENSITY FOR COMPOUND STATES OF NUCLEI

RODIN, VA; URIN, MH

IZVESTIYA AKADEMII NK SERIYA FIZICHESKAYA; vol. 59; issue 5; pp. 7-11; year: 1995

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Coherent backscattering of waves from disordered systems with large-scale inhomogeneities

Rogozkin, DB

LASER PHYSICS; vol. 5; issue 4; pp. 787-792; year: 1995

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LONG-RANGE INTENSITY CORRELA ONS IN WAVE REFLEC ON FROM A DIRDERED MEDIUM

ROGOZKIN, DB; CHERKAV, MY

PHYSICAL REVIEW B; vol. 51; issue 18; pp. 12256-12267; year: 1995

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GIGAN C QUANTUM OSCILLA ONS OF SURFACE IMPEDANCE OF COMPENSATED METALS

SAVELEVA, SN; SKOBOV, VG; CHERNOV, AS

ZHURNAL EKSPERIMENTALNOI I TEORETICHESKOI FIZIKI; vol. 107; issue 5; pp. 1731-1741; year: 1995

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Quantum oscillations of cyclotron absorption in noncompensated metals

Savelvea, SN; Skobov, VG; Chernov, AS

FIZIKA TVERDOGO TELA; vol. 37; issue 11; pp. 3288-3295; year: 1995

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GIANT QUANTUM OSCILLA ONS OF CYCLOTRON ATTENUA NGS IN CADMIUM

SKOBOV, VG; CHERNOV, AS

ZHURNAL EKSPERIMENTALNOI I TEORETICHESKOI FIZIKI; vol. 108; issue 2; pp. 732-740; year: 1995

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STRONG HELICON IN METALS WITH OPEN ORBITS

SKOBOV, VG; CHERNOV, AS

JETP LETTERS; vol. 61; issue 12; pp. 1012-1016; year: 1995

Abstract: The effect of carrier trapping by the field of a large-amplitude rf wave on the electromagnetic properties of precious metals was investigated in a geometry in which open orbits are present. Collisionless absorption by carriers with such orbits is so effective in the linear regime that passage of a helicon through the metal is impossible. It is shown that the trapping of these carriers by the wave held suppresses absorption and makes helicon propagation possible. (C) 1995 American Institute of Physics.

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RELA VE INTENSI ES OF THE DIRECT NUCLEON DECAY OF HIGH-SPIN SUBBARIER SINGLE-PAR CLE STATES IN NEAR-MAGIC NUCLEI

URIN, MH; CHEKOMAZOV, GA

IZVESTIYA AKADEMII NK SERIYA FIZICHESKAYA; vol. 59; issue 5; pp. 2-6; year: 1995

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NONEQUILIBRIUM APPROACH TO DENSE HADRONIC MATTER

VOSKRESENSKY, DN; BLASCHKE, D; ROPKE, G; SCHULZ, H

INTERNA ONAL JOURNAL OF MODERN PHYSICS E-NUCLEAR PHYSICS; vol. 4; Abstract: A general approach to the kinetics of a hadronic many-particle system is formulated employing a nonequilibrium diagram technique. The investigation of medium effects is based on the analysis of the coupled set of nonequilibrium Dyson equations for the pi, N, and Delta components. Some model approaches to their solution are considered. The results are applied to the study of expanding hadronic fireballs containing pions, nucleons, and deltas as produced in the course of heavy-ion collisions at energies provided by the GSI-Sissue up to the CERN-SpS.; pp. 1-45; year: 1995

Abstract: A general approach to the kinetics of a hadronic many-particle system is formulated employing a nonequilibrium diagram technique. The investigation of medium effects is based on the analysis of the coupled set of nonequilibrium Dyson equations for the pi, N, and Delta components. Some model approaches to their solution are considered. The results are applied to the study of expanding hadronic fireballs containing pions, nucleons, and deltas as produced in the course of heavy-ion collisions at energies provided by the GSI-Sissue up to the CERN-SpS.

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EXPONEN AL-GROWTH AND POSSIBLE CONDENSA ON OF THE PAR CLE-HOLE EXCITA ONS IN MOVING HOT FERMI LIQUIDS

VOSKRESENSKY, DN

PHYSICS LETTERS B; vol. 358; issue 1-2; pp. 1-6; year: 1995

Abstract: The production rate of particle-antiparticle and particle-hole excitations in relativistically moving hot Fermi liquids is calculated. The kinetics of the damping of the excitations as well as of the exponential growth of the particle-hole excitations for some regions of space-like momenta is considered, in the center of mass coordinate projected along the quasi-particle current direction. It is shown that Cherenkov-like radiation of the excitations may form a Bose condensate with a non-zero wave vector. Explicit results are presented for pions and for various types of zero sounds in moving hot nuclear matter.

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DIRECT REAC ONS INVOLVING PION-PRODUC ON IN HOT NUCLEAR-MATTER

VOSKRESENSKII, DN; KOLOMEITSEV, EE

PHYSICS OF ATOMIC NUCLEI; vol. 58; issue 1; pp. 126-130; year: 1995

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ON THE DIRECT NUCLEON DECAY OF HIGH-SPIN SUBBARRIER SINGLE-PAR CLE STATES IN NEAR-MAGIC NUCLEI

CHEKOMAZOV, GA; URIN, MH

PHYSICS LETTERS B; vol. 349; issue 4; pp. 400-404; year: 1995

Abstract: The description of the direct nucleon decay of high-spin subbarrier one-particle states in near-magic nuclei is attempted using a simple optical model and the simplest version of the coupled-channel approach. The branching ratios for the direct decay of the several single-neutron states in Pb-209 and Zr-91 to the ground state and to the low-lying collective states of Pb-208 and Zr-90, respectively, are evaluated. Results are compared with recent experimental data.

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NONEQUILIBRIUM DESCRIP ON OF BREMSSTRAHLUNG IN DENSE MATTER (LAND-POMERANCHUK-MIGDAL EFFECT)

KNOLL, J; VOSKRESENSKY, DN

PHYSICS LETTERS B; vol. 351; issue 1-3; pp. 43-49; year: 1995

Abstract: The soft behavior of the bremsstrahlung from a source is discussed in terms of classical transport models and within a non-equilibrium quantum field theory (Schwinger-Kadanoff-Baym-Keldysh) formulation.

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ON A MECHANissueM OF SURFACE OXIDE FORMA ON NEAR THE NUCLEA ON THRESHOLD

BORMAN, VD; GUSEV, EP; DEVYATKO, YN; TRONIN, VN; TROYAN, VI

SURFACE SCIENCE; vol. 301; issue 1-3; pp. L239-244; year: 1994

Abstract: A kinetic theory of submonolayer oxide formation on solid surfaces near the transition point from adsorption to surface oxide growth has been developed. The theory is based on vacancy instabilities of surface layers interacting with oxygen. The driving force onset of the surface oxidation is shown to be spontaneous vacancy generation when the oxygen coverage approaches the critical value. This gives rise to a substantial decrease of the critical radius for oxide islands and consequently to simultaneous oxide phase nucleation.

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DOPPLER-SHIFTED CYCLOTRON-RENANCE IN METALS

CHERNOV, AS; SKOBOV, VG

PHYSICS REPORTS-REVIEW SEC ON OF PHYSICS LETTERS; vol. 244; issue 1; pp. 1-75; year: 1994

Abstract: The Doppler shift of the frequency of a wave field acting on electrons in a metal can be very large: in the rf range it exceeds the frequency by several orders of magnitude. Therefore, in a dc magnetic field perpendicular to the metal surface the cyclotron resonance is shifted into the frequency range which extends from a few kilohertzs up to a few gigahertzs. Unlike the Azbel'-Kaner cyclotron resonance, which is temporal, the Doppler-shifted cyclotron resonance (DSCR) is a spatial resonance. It occurs when the rf wavelength coincides with the extremal displacement of the conduction electrons for one cyclotron period. Owing to Fermi degeneration of the electrons, the DSCR manifests itself as particular components of the electromagnetic field: a doppleron and a Gantmakher-Kaner component. The former is a natural mode of the electromagnetic field in a degenerated plasma of a metal, whose wavelength is close to the extremal displacement of the electrons for a cyclotron period. The latter is also associated with the mentioned electrons, but it is not a natural mode of a plasma. Penetration of the components through a metal slab results in oscillations of the surface impedance of the slab as a function of a dc magnetic field. In this review we present the main results of theoretical and experimental studies of the DSCR in metals carried out during the last three decades. In Part I we describe the properties of dopplerons: their spectra, damping, polarizations, the range of the magnetic field values where they exist, the role of the Fermi surface anisotropy, etc. Part II is devoted to a quantitative description of the excitation of the dopplerons and Gantmakher-Kaner components in metals and to comparison of the theory with experimental data. An important role of the non-specularity of reflection of the conduction electrons from metal surfaces is established. For building the theory, nontrivial methods of solution of the corresponding integrodifferential equations are developed; thus, for example, a method of analytical solution of the two-sided Wiener-Hopf problem is developed. Part III is devoted to nonlinear effects in the DSCR, unexpected for the dense electron plasma in metals. Although the wave field has a little effect on the trajectories of most of the electrons on the Fermi surface, it can significantly alter the motion of the small electron groups responsible for the collisionless wave absorption. When the wave field amplitude is large enough, the electrons are trapped by the field and the collisionless absorption is suppressed. This is valid both for the magnetic Landau damping and for the cyclotron absorption. In the latter case the effect turns out to be so drastic that it results in the appearance of a new doppleron mode which does not exist at small wave field amplitudes. The appearance of the magnetic Landau damping in the case when the wave propagates parallel to a dc magnetic field presents another type of nonlinear effect. It is associated with the fact that the magnetic field of a wave of large amplitude causes the total magnetic field vector to deviate from the wave propagation vector.

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CALCULA ON OF THE CRI CAL-CURRENT OF A JOSEPHN LAT CE TAKING INTO ACCOUNT CORRELA ONS OF PHASES AT ADJACENT PINNING CENTERS

CHERNOV, AS; GORBACHEV, VS; SAVELEV, SE

PHYSICA C; vol. 223; issue 1-2; pp. 62-70; year: 1994

Abstract: A method for calculating the critical current of a Josephson lattice is proposed. The boundary conditions and the correlations of phases at adjacent pinning centers are taken correctly into account. Restrictions are defined on the admissible values of magnetic field and geometrical dimensions of the lattice, at which the current flowing across each contact is close to its maximum. In this situation a general expression for the critical current of an arbitrary lattice is obtained. The special cases of a one-dimensional chain of junctions, of square, of rectangular and of textured lattices are considered.

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DIPOLE MATRIX-ELEMENTS IN THE QUASI-CLASSICAL APPROXIMATION

JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS; vol. 27; issue 19; pp. 4403; year: 1994;

Abstract: The set of analytic formulae with overlapping areas of applicability, enabling approximate calculation of the dipole matrix elements between any quasi-classical states, is presented. In the Coulomb field the energies of the quasi-classical states border on the continuous spectrum limit on two sides and, consequently, these are the matrix elements of the bound-bound, bound-free and free-free transitions that are considered in the review. The analytic formulae are obtained both in the context of and without taking into account the Heisenberg correspondence principle. In the purely Coulomb field a comparison of approximate and exact results is performed. The non-Coulomb character of the atomic potential at small distances is taken into account by introducing the quantum defects and non-Coulomb phases of scattering. Approximate formulae for transitions between the states of the parabolic basis are considered. Quasi-classical results find application in quantitative calculations and qualitative estimations when investigating one-photon radiative transitions, multiphoton excitation and ionization of the Rydberg states, including the problems elated to the above-threshold ionization, stabilization and coherent atomic wavepackets.

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INSTABILITY OF THE AXISYMMETRICAL SHAPE OF 2-DIMENSIONAL NUCLEI AS A FUNC ON OF THE RELAXA ON OF THE ORDER-PARAMETER FIELD

DEVYATKO, YN; ROGOZHKIN, SV; FEDOTOV, BA

PHYSICAL REVIEW B; vol. 50; issue 9; pp. 5857-5864; year: 1994

Abstract: The instability of the shape of two-dimensional new-phase nuclei is studied using an order-parameter field equation. The criteria of instability of angular perturbations are obtained for systems in which the order-parameter nonconservation processes are negligible. These coincide with criteria obtained within the framework of the phenomenological Zeldovich-Volmer theory and the continual diffusion-limited aggregation model in the diffusive limit. The influence of small angular perturbations on the fractal dimensionality of the nuclei is discussed.

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FORMA ON OF INFORMA VE SIGNALS FOR OP CAL COMMUNICA ON AND RANGING BY MEANS OF A DOUBLE-MODE ND-YAG LASER

ERMACHENKO, VM; PANTELEEV, AV; PETROVSKY, VN; PROTSENKO, ED; SHANANIN, RA

IZVESTIYA AKADEMII NK SERIYA FIZICHESKAYA; vol. 58; issue 2; pp. 25-34; year: 1994

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GAS-LASERS WITH INER AL AC VE MEDIUM AND INTERNAL FREQUENCY-MODULA ON

ERMACHENKO, VM; PANTELEEV, AV; PETROVSKY, VN; PROTSENKO, ED; SHANANIN, RA

IZVESTIYA AKADEMII NK SERIYA FIZICHESKAYA; vol. 58; issue 6; pp. 31-39; year: 1994

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INTENSITY OF RADIA ON FROM A 2-MODE HE-NE-LASER WITH EXTERNAL SIGNAL INJEC ON

ERMACHENKO, VM; KORNILOV, ST; PETROV, VV; PROTSENKO, ED

KVANTOVAYA ELEKTRONIKA; vol. 21; Abstract: Theoretical and experimental investigations were made of the reaction of the laser power to an external radiation signal. The laser with an injected signal (Lissue) was an He-Ne laser emitting radiation at the wavelength of 3.39 mum in the form of two orthogonally polarised modes. A study was made of the influence of the frequency detuning of the external signal from the Lissue radiation, and also of the intensities of both radiations on the laser power response.; pp. 1169-1173; year: 1994

Abstract: Theoretical and experimental investigations were made of the reaction of the laser power to an external radiation signal. The laser with an injected signal (Lissue) was an He-Ne laser emitting radiation at the wavelength of 3.39 mum in the form of two orthogonally polarised modes. A study was made of the influence of the frequency detuning of the external signal from the Lissue radiation, and also of the intensities of both radiations on the laser power response.

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COHERENT BACKSCATTERING OF A LIGHT-PULSE BY A SLAbstract: OF DIRDERED MEDIUM

GORODNICHEV, EE; ROGOZKIN, DB

WAVES IN RANDOM MEDIA; vol. 4; issue 1; pp. 51-57; year: 1994

Abstract: We obtain an exact analytical solution to the problem of the enhanced backscattering of a short pulsed signal from a two- and three-dimensional medium with isotropically scattering centres. The angular spectrum is expressed in terms of the solution to the corresponding stationary problem. The intensity oscillations are shown to appear on the tails of the angular spectrum. The origin of these oscillations is associated with the ballistic phase shift between the interfering waves arriving at the detector. It is shown that the finiteness of the slab thickness influences the magnitude of the backscattering intensity and does not change the shape of the angular spectrum. The range of validity for the diffusion approximation is pointed out. The results obtained in the paper also contain a generalization of the well known solution to the problem of incoherent transfer of a pulsed signal to the case of two-dimensional disordered media.

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1/N-DECOMPOSI ON OF WAVE-FUNCTIONS

KARNAKOV, BM; MUR, VD; POPOV, VS

ZHURNAL EKSPERIMENTALNOI I TEORETICHESKOI FIZIKI; vol. 106; issue 4; pp. 976-992; year: 1994

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ANGULAR-DissueTRIBU ONS OF MUL PLY SCATTERED LASER-RADIA ON IN WEAKLY Abstract:RBING MEDIA WITH LARGE-SCALE SCATTERING CENTERS

KUZOvol.EV, AI; REMIZOVICH, VS

LASER PHYSICS; vol. 4; issue 4; pp. 788-815; year: 1994

Abstract: Dependence of the angular distribution of laser radiation on the regime of single scattering is analyzed in a standard small-angle approximation. The contributions of scattering amplitudes of various multiplicities to the formation of the radiation angular spectrum is considered. It is shown that the number of scattering events contributing to the radiation spectrum is considerably larger than the mean number of collisions in the scattering layer. The radiation angular spectrum behavior at relatively large depths is analyzed. In this case, the diffusion or quasi-diffusion approximation in angular space is shown to be valid, depending on the rate of the phase function decrease with the increase of the single-scattering angle. For the phase functions decreasing with the increase of the scattering angle according to the power law, the radiation angular spectrum is shown to decrease according to the same law as the phase function at relatively large scattering angles. The results of calculations are presented graphically for various model phase functions.

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DESCRIP ON OF RELA Vissue C HEAVY-LIGHT QUARK-AN QUARK SYSTEMS VIA DIRAC-EQUA ON

MUR, VD; POPOV, VS; SIMONOV, YA; YUROV, VP

ZHURNAL EKSPERIMENTALNOI I TEORETICHESKOI FIZIKI; vol. 105; issue 1; pp. 3-27; year: 1994

Abstract: Starting from the QCD Lagrangian and taking into account both perturbative and nonperturbative effects, we use the method of vacuum correlators to derive the Dirac equation (rigorously for the Coulomb interaction and heuristically for the confining potential) for a system consisting of a light quark and heavy antiquark. As a result the confining potential is a Lorentz scalar, and the Coulomb part is the fourth component of a 4-vector. The energy spectrum of the Dirac equation is considered for these potentials. Numerical calculations of energy eigenvalues E = E(nkappa) are performed, and some exact solutions of the Dirac equation in the case E = 0 are found. An effective-potential method convenient for qualitative study of the solution of the Dirac equation is developed. The connection with experimental spectra of D- and B-mesons is briefly discussed.

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N-ALPHA SCATTERING IN THE VICINITY OF THE HE-5-ASTERissueK RENANCE

MUR, VD; KARNAKOV, BM; POZDNYAKOV, SG; POPOV, VS

PHYSICS OF ATOMIC NUCLEI; vol. 57; issue 5; pp. 769-774; year: 1994

Abstract: The amplitude of nalpha scattering in the vicinity of the He-5(*) (3/2+) resonance is expressed in terms of the scattering length and effective range of the dt system. The total cross section of scattering near the threshold of the dt channel is compared with experimental data. It is shown that the phase shift analysis of elastic nalpha scattering at these energies is an effective method for choosing the low-energy parameters of the dt system.

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PAR AL ESCAPE WIDTHS OF GIANT-RENANCES

MURAVIEV, SE; URIN, MH

NUCLEAR PHYSICS A; vol. 572; issue 2; pp. 267-293; year: 1994

Abstract: A method for calculation of the partial-nucleon-escape widths of giant resonances is proposed. The method is exact within the random-phase approximation in the continuum. A phenomenological description of the giant-resonance coupling to many-particle configurations is also given. This approach is applied to evaluation of the partial-nucleon-escape widths of various giant resonances in Pb-208 parent nucleus. Our results are compared with the results of other theoretical approaches and with the relevant experimental data.

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PAR AL NUCLEON ESCAPE WIDTHS OF GIANT-RENANCES

MURAVIEV, SE; URIN, MH

NUCLEAR PHYSICS A; vol. 569; issue 1-2; pp. C267-270; year: 1994

Abstract: Method and results of calculation of the partial nucleon escape widths of various giant resonances are presented. The comparison with relevant experimental data and the results of other theoretical approaches is given where it is possible. The partial widths for the direct proton decay of the Gamow-Teller resonance in Sn isotopes are given special attention.

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PERTURBA ON-THEORY FOR QUASI-STA ONARY LEVELS

POPOV, VS; MUR, VD

JETP LETTERS; vol. 60; issue 1; pp. 66-70; year: 1994

Abstract: A perturbation-theory formula is derived for the energies of quasistationary states (resonances) in the semiclassical approximation. This formula is valid for resonances either below or above the barrier. It is illustrated for several potentials, for which a comparison can be made with exact solutions.

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CRI CAL FIELDS AND Abstract:OVE-BARRIER STARK RENANCES

POPOV, VS; MUR, VD; SERGEEV, AV

JETP LETTERS; vol. 59; issue 3; pp. 158-162; year: 1994

Abstract: Exact values of the critical field E(c) are calculated for a hydrogen atom, including the case of the ground state. The widths GAMMA(n) of Stark resonances at E = E(c) are also calculated. In the above-barrier region (E > E(c)) the widths GAMMA(n)(E) are essentially linear functions of the electric field strength.

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CRI CAL ELECTRIC-FIELDS AND STARK RENANCES IN THE HYDROGEN-ATOM

POPOV, VS; MUR, VD; SERGEEV, AV

PHYSICS LETTERS A; vol. 193; issue 2; pp. 159-164; year: 1994

Abstract: The exact values of critical electric fields E(c) for different states of a hydrogen atom, including its ground state, as well as the widths Gamma(n) of the Stark resonances at E = E(c), are calculated (at E=E(c)(n(1), n(2), m) the potential barrier for an electron in the (n(1), n(2), m) state disappears). Using the modified quantization condition with barrier penetrability included, we explain the dependence of Gamma(n) on the principal quantum number n.

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THEORY OF STARK-EFFECT IN THE STRONG-FIELD - CRI CAL FIELDS, Abstract:OVE-BARRIER RENANCES, DEPENDENCE ON DIMENSIONAL SCALING

POPOV, VS; MUR, VD; SERGEEV, AV

ZHURNAL EKSPERIMENTALNOI I TEORETICHESKOI FIZIKI; vol. 106; issue 4; pp. 1001-1030; year: 1994

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ON THE ASYMPTO CS OF HIGH-ORDER TERMS OF THE 1/N EXPANSION

POPOV, VS; SERGEEV, AV; MUR, VD; SHCHEBLYKIN, AV

PHYSICS OF ATOMIC NUCLEI; vol. 57; issue 6; pp. 1057-1065; year: 1994

Abstract: Analytic and numerical methods for determining the asymptotics of high-order terms of the 1/n expansion in quantum-mechanical problems are developed. It is shown that this asymptotics is always of the factorial type. The dependence of parameters of the asymptotics on the form of the potential and on the coupling constant is especially analyzed in the vicinity of the point of collision of classical solutions.

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CON NUUM RANDOM-PHASE-APPROXIMA ON SELF-CONSissueTENT APPROACHES TO THE THEORY OF IBARIC ANALOG RENANCES

RUMYANTSEV, OA; URIN, MH

PHYSICAL REVIEW C; vol. 49; issue 1; pp. 537-540; year: 1994

Abstract: Two approaches (exact and approximate) to the isobaric analog resonance (IAR) theory within the random phase approximation in the continuum are considered. Both of them are based on the partial self-consistency condition which is the result of the isospin symmetry of the nuclear Hamiltonian. The evaluations of the IAR partial proton widths for near magic nucleic over a wide atomic mass region are performed. The results obtained within the framework of these approaches are compared with each other and with the experimental data. The method of the calculation of the Coulomb correction to the IAR transition density is also given.

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THE MANY-PHONON COUPLED-CHANNEL APPROACH AND THE ANALYSissue OF LOW-ENERGY NEUTRON-SCATTERING BY SPHERICAL NUCLEI

SAMOILOV, VV; URIN, MH

NUCLEAR PHYSICS A; vol. 567; issue 2; pp. 237-265; year: 1994

Abstract: A way to solve the system of equations of the traditional coupled-channel approach (CCA) by means of the Green-function method is proposed. A many-phonon CCA version is formulated within the harmonic (for the phonons) approximation. Within this version the A-dependence of the s- and p-neutron strength functions and scattering radii, the anisotropy parameters of the angular distribution and the polarization for the elastic scattering, the total inelastic-scattering cross section (to the first 2(+) level) are calculated. It is shown that for many nuclei it is necessary to take into account the coupling of single-particle states to many-phonon ones and for these nuclei the mentioned characteristics are slightly dependent on the strength of the imaginary part of the optical potential.

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EFFECT OF THE GIANT QUANTUM OSCILLA ONS OF LAND MAGNE C DAMPING ON THE COMPENSATED METAL-SURFACE IMPEDANCE

SKOBOV, VG; FissueUNENKO, AL; CHERNOV, AS

FIZIKA TVERDOGO TELA; vol. 36; issue 6; pp. 1606-1609; year: 1994

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SEMIMICROSCOPIC APPROACH TO THE THEORY OF SEMIDIRECT PHOTONUCLEON REAC ONS

URIN, MH; CHEKOMAZOV, GA

IZVESTIYA AKADEMII NK SERIYA FIZICHESKAYA; vol. 58; issue 11; pp. 80-88; year: 1994

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POTEN ALITY OF PIOMEN BOSE-CONDENSA ON IN ULTRARELA Vissue C COLLissueIONS OF NUCLEI

VOSKRESENSKII, DN

ZHURNAL EKSPERIMENTALNOI I TEORETICHESKOI FIZIKI; vol. 105; issue 6; pp. 1473-1497; year: 1994

________________________________________

 

ON THE P-ODD EFFECT AT THE INTERAC ON OF POLARIZED NEUTRONS WITH NUCLEI

VYAZANKIN, ON; URIN, MH

IZVESTIYA AKADEMII NK SERIYA FIZICHESKAYA; vol. 58; issue 2; pp. 218-221; year: 1994

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INSTAbstract:ILITY OF HOMOGENEOUS DissueTRIBU ON OF RADIA ON DEFECTS IN METALS IN THE CASE OF HEAVILY FLUCTUA NG DEFECT PRODUC ON

DEVYATKO, YN; MAKLETV, AA; TRONIN, VN

NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SEC ON B-BEAM INTERAC ONS WITH MATERIALS AND ATOMS; vol. 80-1; pp. 102-105; year: 1993

Abstract: The phase transition to the inhomogeneous state in the system of interacting point defects in metals was investigated previously in terms of stability analysis of the homogeneous solution of the diffusion-type equations with constant defect production rate. The effective defect production rate for cascade inducing irradiation is shown to fluctuate heavily. An effective order parameter equation based on the appropriate equations with fluctuating defect production rate is obtained. Correlation functions of the fluctuations yield the nonlocal terms in the order parameter equation, thus producing the effective defect interaction ''via fluctuations''. The solutions demonstrate the change of the phase transition condition and the drastic increase of defect concentration in the growing new phase bubble.

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FORMA ON OF THE NEW PHASE issueLANDS ON THE SURFACE AS THE ORDER PARAMETER RELAXA ON

DEVYATKO, YN; ROGOZHKIN, SV; MUSIN, RN; FEDOTOV, BA

ZHURNAL EKSPERIMENTALNOI I TEORETICHESKOI FIZIKI; vol. 103; issue 1; pp. 286-300; year: 1993

Abstract: The growth kinetics of new phase two-dimensional islands is studied with the help of the equation of order parameter field. The island growth equations are derived in the various regimes. The connection of the approach developed with the Zel'dovich -Folmer phenomenological theory is found. The appearance of the different types of the island boundary conditions used in the phenomenological theory is analyzed.

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INSTAbstract:ILITY OF THE AXIAL FORM FOR 2-DIMENSIONAL issueLANDS OF NEW PHASE IN THE GINZBURG-LAND THEORY

DEVYATKO, YN; ROGOZHKIN, SV; FEDOTOV, BA

ZHURNAL EKSPERIMENTALNOI I TEORETICHESKOI FIZIKI; vol. 104; issue 1; pp. 2556-2573; year: 1993

Abstract: The instability of the azimuthal form for two-dimensional islands of new phase is Studied by means of the equation for the field of Ginzburg-Landay-like order parameter. The diagrams for instability of angle perturbations are found and the instability is shown to occur provided the main growth mechanism is diffusive. The region of parameters where the criteria obtained coincide with the results of the phenomenological Zeldovich-Former theory and continual diffusion limited aggregation model is determined. The criteria for the growth of angle perturbations are studied in caw of the nonstationary growth regime are analyzed. The effect of angle perturbation of the form on the value of the cluster fractal dimension is considered.

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The Dynamics and Radiation of a Relativistic Electron in the Field of an Intense, Focused Laser Pulse

Goreslavskii, SP; Narozhny, NB; Shcherbachev, OV; Yakovlev, VP

LASER PHYSICS; vol. 3; issue 2; pp. 418-430; year: 1993

Abstract: The effect of the field-induced broadening of harmonics radiated by an electron in the field of a high-intensity focused laser pulse was investigated. Broadening is caused by ponderomotive scattering, which continuously changes the average velocity of the electron and thus modulates the Doppler frequency shift of harmonics in the laboratory frame of reference. At relativistic intensities, broadened harmonics overlap, yielding a continuous radiation spectrum. This paper proposes a modification of the averaging procedure, which yields equations governing the averaged motion of an electron in the strong field of a focused pulse, with the dimensionless intensity parameter higher than, or of the order of, unity.

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FRAGMENTA ON OF GAMOW-TELLER STRENGTH OBSERVED IN SN-117,SN-120(HE-3,T)SB-117,SB-120 CHARGE-EXCHANGE REAC ONS

JANECKE, J; PHAM, K; ROBERTS, DA; STEWART, D; HARAKEH, MN; BERG, GPA; FOSTER, CC; LissueANT , JE; SAWAFTA, R; STEPHENN, EJ; VANDENBERG, AM; VANDERWERF, SY; MURAVIEV, SE; URIN, MH

PHYSICAL REVIEW C; vol. 48; issue 6; pp. 2828-2839; year: 1993

Abstract: The (He-3,t) charge-exchange reaction has been studied at E(He-3) = 200 MeV and angles near 0-degrees on targets of Sn-117 and Sn-120. Fragmentation of the giant Gamow-Teller resonance into separate components of the particle-hole type has been observed in good agreement with theoretical predictions. These components are connected with what is usually referred to in the literature as direct-, core-polarization-, and back-spin-flip Gamow-Teller strength. The observed cross sections near theta = 0-degrees suggest contributions from the isovector spin-flip interaction as well as the isovector tensor interaction. A theoretically predicted configuration splitting of the main Gamow-Teller component into two components involving the 1h11/2 neutron orbital could not uniquely be identified. The data are compatible, though, with such a splitting since the observed widths of the main Gamow-Teller components in Sb-117 and Sb-120 exceed the predicted splittings.

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N-14 AND C-13 NMR OF ITOPE PARAMAGNE C SHIFT IN NICKEL AND COBALT COMPLEXES

KESSENIKH, AV; ATAEV, A; PLAKHU N, BN; FEDOTOV, MA

KHIMICHESKAYA FIZIKA; vol. 12; issue 12; pp. 1687-1696; year: 1993

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TUNNELING OF FAST CHARGED-PAR CLES THROUGH THE SUBSTANCE IN MAGNE C-FIELDS

KOVALEV, SD; KUZOvol.EV, AI; ROGOZKIN, DB

ZHURNAL TEKHNICHESKOI FIZIKI; vol. 63; issue 6; pp. 27-46; year: 1993

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AVERAGE ENERGY-LOSSES OF REFLECTED AND TRANSMITTED PAR CLES IN THE CASE OF A GRAZING INCIDENT BEAM STRIKING A FLAT SCATTERER OF FINITE THICKNESS

KUZOvol.EV, AI; REMIZOVICH, VS

PHYSICAL REVIEW A; vol. 48; issue 1; pp. 465-470; year: 1993

Abstract: The problem is considered of small-angle reflection and transmision of charged particles in the case of grazing incidence of a broad beam upon the surface of a flat scatterer of finite thickness. Simple analytical expressions are obtained for the average energy loss of reflected and transmitted particles taking into account mutual correlation between scattering and transmission processes.

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LOW-ENERGY PARAMETERS OF THE DT AND DHE-3 SYSTEMS

MUR, VD; KARNAKOV, BM; POZDNYAKOV, SG; POPOV, VS

PHYSICS OF ATOMIC NUCLEI; vol. 56; issue 2; pp. 217-226; year: 1993

Abstract: For resonance Coulomb systems a bound on the effective range r(l)(cs) at the instant of appearance of the l level (a(l)(cs) = infinity) is derived for arbitrary angular momentum. For s states this bound is generalized to the case of finite values of the scattering length. The bound is used to calculate the scattering lengths and effective ranges of the d H-3 and d He-3 systems on the basis of the effective-range expansion and the experimental data on the cross sections for fusion reactions.

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QUAN ZA ON RULES FOR Abstract:OVE-BARRIER RENANCES

MUR, VD; POPOV, VS

JETP LETTERS; vol. 57; issue 7; pp. 418-422; year: 1993

Abstract: The Bohr-Sommerfeld quantization condition is analytically continued into the above-barrier region. The result is used to find the asymptotic behavior of the energies of resonances under strong-coupling conditions.

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The Stark Effect in Strong Fields: Perturbation Theory, 1/n-Expansion and Scaling

Mur, VD; Popov, VS

LASER PHYSICS; vol. 3; issue 2; pp. 462-474; year: 1993

Abstract: The theory of the Stark effect in strong fields that are comparable with an atomic field at the electron orbit is reviewed. The following questions are considered: divergence of the series of the perturbation theory and the methods of their summing (including series with constant signs), 1/n-expansion, the quantum defect, and scaling relationships for near-threshold resonances. Theoretical calculations of Stark shifts and widths of atomic levels, as well as scaling relationships, agree well with the experimental data.

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WKB METHOD FOR RENANCES

MUR, VD; POPOV, VS

ZHURNAL EKSPERIMENTALNOI I TEORETICHESKOI FIZIKI; vol. 104; issue 1; pp. 2293-2313; year: 1993

Abstract: For the potentials with a barrier the analytical continuation of the Bohr - Sommerfeld quantization rule into the region of overbarrier resonances is derived. The equations obtained are valid for an arbitrary analytical potential satisfying the quasiclassical conditions and determine both the position of resonance E(r) and its width GAMMA. The results are demonstrated for a number of model potentials and also for the Stark effect in a strong field. The energy asymptotic of resonances in the strong coupling regime is found.

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INTERFERENCE EFFECTS IN LIGHT BACKSCATTERING BY A SYSTEM OF BROWNIAN PAR CLES

ROGOZKIN, DB

PHYSICA B; vol. 191; issue 3-4; pp. 348-354; year: 1993

Abstract: The present study is devoted to a weak localization problem in multiple wave scattering by a system with a dynamical disorder. The general expression for spectral and angular distribution of backscattered waves is obtained. The J(c)(f, theta) spectrum (f is the frequency shift due to multiple quasi-elastic scattering, theta is the angle of deviation from the exact backward direction) is expressed in terms of the exact solution of the coherent albedo problem for fixed scatterers. Wave scattering in media with a dynamical disorder caused by diffusion of scattering particles, their ballistic motion and excitation of the internal degrees of freedom is discussed. The line shape of the backscattering spectrum is analyzed. In the case where the particle motion is diffusive, the interference contribution at the wings of the spectral line falls off as f-5/2. If the ballistic type of phase breaking dominates then the wings of backscattered intensity is suppressed in accordance with the exponential law.

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INTENSITY CORRELA ON IN A DIRDERED MEDIUM WITH LARGE SCATTERERS

ROGOZKIN, DB; CHERKAV, MY

PHYSICS LETTERS A; vol. 178; issue 5-6; pp. 431-439; year: 1993

Abstract: We consider the long-range intensity correlation in a speckle pattern. We find an analytical solution for the intensity correlation function for the case of a plane wave propagation through a random slab with large scatterers (their size a is much larger than the wavelength lambda). Both single and multiple wave scattering are assumed to have a sharply anisotropic (small-angle) character. The qualitative differences between the intensity correlations in a disordered medium with purely elastic scattering and those in an absorbing medium are analyzed in detail.

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LONG-RANGE INTENSITY CORRELA ONS IN THE BACKSCATTERING OF LIGHT FROM DIRDERED MEDIA

ROGOZKIN, DB; CHERKAV, MY

JETP LETTERS; vol. 58; issue 8; pp. 585-591; year: 1993

Abstract: Long-range intensity correlations in the speckle patterns formed by coherent light reflected from a multiple-scattering medium are analyzed. In the case of purely elastic scattering, one should see a triangular dip in the fluctuation spectrum.

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ON THE PARITY VIOLA ON EFFECT IN THE SCATTERING OF LOW-ENERGY POLARIZED NEUTRONS FROM NUCLEI

URIN, MH; VYAZANKIN, ON

PHYSICS LETTERS B; vol. 305; issue 3; pp. 187-189; year: 1993

Abstract: Within the framework of the valence mechanism of the mixing Of p1/2 and s1/2 compound resonances due to the parity-violating part of the nuclear mean field, a quantitative estimate is given for the corresponding contribution to the parity-violating asymmetry. The estimation is based on the use of an optical model. The estimated value is found to be essentially less than a value extracted from experimental data for the Th-233 compound nucleus.

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DissueTRIBU ON OF VACUUM CHARGE IN THE PRESENCE OF STA C ELECTRIC-FIELD URCES IN QED AND THE GLUOELECTRIC FIELD IN QCD

VOSKRESENSKII, DN

PHYSICS OF ATOMIC NUCLEI; vol. 56; issue 2; pp. 232-236; year: 1993

Abstract: The electric-field distribution in QED and the gluoelectric-field distribution in QCD are determined near the corresponding static external sources. These field distributions are determined by the free and bound charges present in the vacuum as a result of the presence of the sources. The distributions of the electric and gluoelectric fields near two static sources of equal and opposite electric and color charge are also determined with allowance for the dielectric properties of the vacuum, as well as the electron and quark condensate.

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DIRECT REAC ONS WITH PION-PRODUC ON IN NUCLEUS-NUCLEUS COLLissueIONS

VOSKRESENSKII, DN; KOLOMEITSEV, EE

PHYSICS OF ATOMIC NUCLEI; vol. 56; issue 2; pp. 252-259; year: 1993

Abstract: Various processes of pion production in nuclear matter at characteristic temperatures T much less than m(pi) are analyzed. It is shown that the pions are produced mainly in NN --> NN(pi) reactions. Taking into account the modification of the NN interaction in nucelar matter, probabilities and differential cross sections of production of pi- mesons in direct NN --> NNpi- reactions are calculated. It is shown that at incident-pion momenta q approximately 2m(pi) processes with pion production via DELTA-resonance intermediate states dominate. From a comparison of the results of the calculation with experimental data on pion production in nucleus-nucleus collisions it is concluded that piN absorption is strong and increases with increasing temperature and density of the nuclear matter. At the initial stage of development of the nuclear fireball the pions are confined inside the system at practically all momenta. Soft (q less-than-or-similar-to m(pi)) pions are emitted at the intermediate stage of expansion of the nuclear fireball, and harder pions are released together with nucleons at the final stage of breakup of the fireball.

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MANY-PAR CLE EFFECTS IN NUCLEUS-NUCLEUS COLLissueIONS

VOSKRESENSKY, DN

NUCLEAR PHYSICS A; vol. 555; issue 1; pp. 293-328; year: 1993

Abstract: Migdal's theory of finite Fermi systems is applied for the description of nucleus-nucleus collisions at laboratory energies less than a few GeV/A. It is taken into account that the pionic degree of freedom softens in nuclear matter. Free paths of nucleon and pion quasiparticles are calculated. Compact formulas are written for pion, nucleon- and photon-production cross sections. In addenda, the main formulas are presented for the NN-interaction amplitude and pion polarization operator in non-equilibrium and heated equilibrium nuclear matter.

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QUASI-CLASSICAL DESCRIP ON OF CONDENSED SYSTEMS BY A COMPLEX-ORDER PARAMETER

VOSKRESENSKY, DN

PHYSICA SCRIPTA; vol. 47; issue 3; pp. 333-354; year: 1993

Abstract: A quasiclassical description of condensed systems is given in terms of a complex order parameter psi interacting with a gauge field A(mu). The order parameter psi can relate as to the conserving as to the non-conserving number of corresponding particles. The electromagnetic field as well as the deformation field of the specific type may take a part of the gauge A(mu)-field. The phenomenological Lagrangian of the model is constructed in the coordinate representation. The parameters of the Lagrangian are expressed in terms of the medium polarization function. The transition from the given psi order parameter to the quasiclassical variables, Absolute value of psi 2 and delS, where psi = Absolute value of psi e(iS), is performed for the general case of the non-conserving particle number. Equations obtained are formally analogous to the Navier-Stokes equation and to the continuity equation. The latter, however, consists of some particle source in the r.h.s. The principal question on the possibility of the description of systems with dissipation in terms of macroscopic psi-function is raised and positively solved. The transition from the obtained equations for the macroscopic wave function to the hydrodynamical variables is also performed. The first and the second viscosities are expressed in terms of the medium polarization function. It is shown that the inhomogeneous phase (k not-equal 0) is described by anisotropic hydrodynamical equations. The hydrodynamical equations are reduced to more simple equations describing the relaxation of the new order parameters. As an example, the dynamics of the non-conserving order parameter in the homogeneous system, which undergoes the first order phase transition from the metastable state to the stable one, is considered in detail. The question how the weakly non-spherical overcritical germs acquire the spherical shape during their evolution is studied. It is shown that some essentially non-spherical initial configurations have significantly smaller critical size than the spherical ones and they conserve the shape during their growth to the new phase. The static inhomogeneous configurations of the one-axis systems and the configurations of the anisotropic three-dimensional lattices are studied. The dynamics of the first order phase transition to the inhomogeneous condensed state is considered. It is shown that this dynamics is essentially anisotropic. Different initial configurations have the distinct critical sizes and their evolution is characterized by the various velocities. Achieved dynamical description allows to understand the physical picture of the process of the monocrystal and the polycrystal growth. A possible description of the glassing and amorphouzation processes as the phase transitions from the lability region to some heterogenic inhomogeneous (k not-equal 0) state is discussed. The problem of the domain sticking in the polycrystals is considered. The dynamics of the process of the material aging is also discussed in the framework of the given model.

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CONDENSATE WITH UL MATE PULSE IN MOVING MEDIUM

VOSKRESENSKII, DN

ZHURNAL EKSPERIMENTALNOI I TEORETICHESKOI FIZIKI; vol. 104; issue 6; pp. 3982-4009; year: 1993

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STA S CAL CALCULA ONS OF FREE-ENERGY OF ADRBED ATOM SYSTEM

DEVYATKO, YN; MUSIN, RN; ROGOZHKIN, SV

IZVES YA AKADEMII NK SSSR SERIYA FIZICHESKAYA; vol. 56; issue 6; pp. 125-129; year: 1992

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Field-Induced Broadening of the Spontaneous Emission Spectrum of an Electron in a Strong Light Field

Goreslavsky, SP; Narozhnyi, NB; Shcherbachev, OV; Yakovlev, VP

LASER PHYSICS; vol. 2; issue 6; pp. 1025-1027; year: 1992

Abstract: It is shown that the space-time inhomogeneity of a strong light field is the chief cause of broadening of harmonics of the spontaneous radiation of an electron which oscillates in this field. The mechanism giving rise to broadening is a modulation of the Doppler shift of the harmonic frequency by the ponderomotive scattering.

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QUANTUM INTERFERENCE PHENOMENA IN ELECTRON BACKSCATTERING BY A RANDOM MEDIUM IN A MAGNE C-FIELD

GORODNICHEV, EE; ROGOZKIN, DB

PHYSICA B; vol. 179; issue 4; pp. 312-316; year: 1992

Abstract: Electron enhanced backscattering in a uniform magnetic field H is studied. Under weak localization conditions (p0l much greater than 1, p is the electron moment, l is the mean free path), an analytical expression for the angular spectrum of backscattered electrons is found. The various H orientations (Hn = 0, [Hn] = 0, n is the normal to a surface) in the cases of 2D- and 3D-disordered semi-infinite systems are considered. It is shown that the quantum interference destruction in a magnetic field gives rise to blunting of the backscattering peak. We have found asymmetry of the angular spectrum and unexpected peak deviation from the exact backward direction. The angular deviation is determined by the average magnetic flux through the contour formed by electron time-reversed trajectories. Generalization of the results, taking into account inelastic electron collisions, is also discussed.

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Radiation Reflection and Transmission in the Case of Grazing Incidence of a Laser Beam upon a Flat Bounded Medium with Large-Scale Scattering Centers

Kuzovlev, AI; Remizovich, VS

LASER PHYSICS; vol. 2; issue 3; pp. 262-287; year: 1992

Abstract: The problem of small-angle light reflection and transmission in the case of grazing incidence of a laser beam upon the surface of a flat bounded medium with strongly anisotropic scattering is considered. The analytical solution to the radiative transfer equation in the Fokker-Plank approximation with respect to scattering angles for the conservative medium is obtained. Simple analytical expressions for the differential coefficients of radiation reflection and transmission with respect to polar angle are derived. The azimuthal angle mean square for both the reflected and transmitted photons, and the total coefficients of radiation reflection and transmission are calculated.

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EFFEC VE IMPURITY MASS IN A FERMI-LIQUID

MESHAKIN, VI; OSADCHIEV, VM

FIZIKA TVERDOGO TELA; vol. 34; issue 9; pp. 2758-2765; year: 1992

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LOW-ENERGY SCATTERING PARAMETERS FOR RENANCE COULOMB-SYSTEMS

MUR, VD; KARNAKOV, BM; POZDYNAKOV, SG; POPOV, VS

JETP LETTERS; vol. 56; issue 3; pp. 127-131; year: 1992

Abstract: A formula for the nuclear-Coulomb effective radius r(l)(sc) has been obtained. This formula can be used for an arbitrary angular moment l and for establishing constraints on the quantity r(l)(cs) which do not depend on the form of the strong potential. The scattering lengths and the effective radii for the lightest hadron systems have been calculated.

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ON THE DIRECT NUCLEON DECAY OF GIANT-RENANCES

MURAVIEV, SE; URIN, MH

PHYSICS LETTERS B; vol. 280; issue 1-2; pp. 1-4; year: 1992

Abstract: A method is proposed for calculating the partial nucleon widths of giant resonances basing on the random phase approximation in the continuum. Within the framework of this method the partial neutron widths of the isoscalar monopole giant resonance in the nucleus Pb-208 were calculated. These results are compared with experimental data and with the results obtained within other theoretical approaches.

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Reflection of Laser Radiation from the Absorbing Medium with Large-Scale Scattering Centers in the Case of Grazing Incidence

Remizovich, VS

LASER PHYSICS; vol. 2; issue 1; pp. 40-57; year: 1992

Abstract: The problem of small-angle light reflection in the case of grazing incidence of a laser beam on the surface of a semi-infinite turbid medium with large-scale scattering centers is considered. The analytical solution to the radiative transfer equation in the Fokker-Plank approximation with respect to scattering angles is obtained. Relatively simple analytical expressions for back-scattered differential coefficients over polar and azimuthal photon reflection angles are derived. The temporal characteristics of the reflected signal are calculated and analyzed. The albedo of the semi-infinite scattering and absorbing medium in the case of grazing incidence of radiation is calculated.

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Propagation of a Laser Pulse in Turbid Medium in the Case of Oblique Incidence of the Broad Beam

Remizovich, VS; Shekhmametyev, SA

LASER PHYSICS; vol. 2; issue 3; pp. 252-261; year: 1992

Abstract: The problem of the propagation of incoherent laser radiation in the case of oblique incidence of the broad beam on the surface of an optically homogeneous medium with strongly anisotropic scattering is considered. The Green's function of the nonstationary transfer equation is obtained in the small-angle diffusion approximation. Simple analytical expressions for the radiation intensity are derived and the cases of stationary and delta-pulsed signals are analyzed in detail. Comparison is made with previously obtained results.

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Intensity Fluctuations of Coherent Radiation in a Disordered Medium with Large Scattering Centers

Rogozkin, DB; Cherkasov, AY

LASER PHYSICS; vol. 2; issue 5; pp. 722-737; year: 1992

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Long-Range Intensity Correlations in a Disordered Medium with Strong Discrete Scatterers

Rogozkin, DB; Cherkasov, MY

LASER PHYSICS; vol. 2; issue 6; pp. 913-927; year: 1992

Abstract: The long-range intensity correlations in a speckle pattern formed by multiply scattered waves are considered. For strong scatterers the fourth Moment equation is derived. An analytical solution is found for long-range correlations both in purely elastic scattering and in the case of absorbing centers.

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MAIN CHARACTERissue CS OF MUON-CAPTURE IN MEDIUM AND HEAVY-NUCLEI

URIN, MH; VYAZANKIN, ON

NUCLEAR PHYSICS A; vol. 537; issue 3-4; pp. 534-550; year: 1992

Abstract: Within the framework of the shell-optical model, a quantitative interpretation of the main characteristics of muon capture from the mesoatom 1s-shell in medium and heavy nuclei is given. The above characteristics are: the capture rate, the various strength functions, and the yield of direct and semidirect neutrons. The parameters of the model are fixed from independent data. The possibility of a substantial renormalization of the form factor of the induced pseudoscalar lepton-nucleon interaction is taken into account. The results of the calculations are compared with the prediction obtained within other theoretical approaches and with the corresponding experimental data. In particular, this comparison permits one to obtain a realistic estimate for the renormalization of the axial part of the lepton-nucleon interaction in nuclei.

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MANIFESTA ON OF POLARIZA ON EFFECTS OF THE NUCLEAR MEDIUM IN NUCLEUS-NUCLEUS COLLissueIONS

VOSKRESENSKII, DN

SOVIET JOURNAL OF NUCLEAR PHYSICS-USSR; vol. 55; issue 2; pp. 202-225; year: 1992

Abstract: The results of the thermodynamical approach to the description of nuclear collisions at energies below a few GeV/nucleon with inclusion of polarization effects of the heated nuclear medium are presented. Arguments are given for the need to include collective effects. The initial scenario of the nucleus-nucleus collision based on the model of an expanding nuclear fireball is formulated. Mean free paths of the nucleon and pion quasiparticles are calculated with allowance for collective effects in the heated nuclear medium. It is found that they are considerably shorter than those predicted by the gas model. The effects of softening of the pion degree of freedom in the nuclear medium in the dynamics of expansion of the nuclear fireball are taken into account. Compact expressions are derived for the differential cross sections for pion production with inclusion of the effects of the medium in its fast breakup. The effects of softening of the pion degree of freedom are taken into account in calculations of the thermodynamical characteristics of the system. By comparing the theoretical and experimental data, the phenomenological equation of state of the heated dense nuclear matter is reproduced. Occupation of the pion and DELTA-isobar branches of the spectrum of pion excitations at T not-equal 0, as well as the existence of the liquid phase of the pion condensate at rho > rho(c1) approximately 0.5-0.7-rho-0(rho-0 congruent-to 0.17 fm-3 is the nuclear density), which corresponds to the appearance of a large number of virtual pion quasiparticles with nonzero momentum (k not-equal 0) corresponding to the low-lying spin-isospin branch of excitations, are taken into account. In accordance with experiment, the compressibility of cold nuclear matter is taken to be equal to 210 MeV. The role of the polarization effects of the nuclear medium in calculating the yields of nucleons is examined. The puzzle of the large entropy is solved in principle. The role of the medium effects in production of photons, whose mean free path is longer than that of the pions and nucleons, is studied. The mean free path of the photons is determined. It is found that high-frequency photons (omega > T) are emitted during the hot initial stage of a nuclear collision. Their differential cross sections are determined by the total NN interaction amplitude in the nuclear medium. In a certain frequency interval (omega < T) the photons are confined inside the nuclear fireball before its breakup. The principal expressions determining the NN interaction amplitude and the pion polarization operator in a heated dense nuclear medium with equal isotopic contents (N = Z) are given in appendices.

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ZERO CHARGE OR ASYMPTO C FREEDOM IN QUANTUM ELECTRODYNAMICS

VOSKRESENSKII, DN

SOVIET JOURNAL OF NUCLEAR PHYSICS-USSR; vol. 55; issue 7; pp. 1090-1098; year: 1992

Abstract: Arguments are given for the condensation of electrons from the lower continuum in the field that arises at ultrashort distances from a positively charged center. In the quasiclassical approximation an equation is derived for the vacuum-charge distribution near a bare charge source of arbitrary radius with allowance for the dielectric properties of the vacuum (epsilon(ren) not-equal 1) and electron condensation. Near a source with radius r0 < r(epsilon) congruent-to m-1 exp [-3pi/2e2 ], (e2 = 1/137) electrons from the lower continuum condense, while for r0 > r(m) greater than or similar to r(epsilon)(r(m) approximately r(epsilon)exp[3piZ(obs)/square-root 2(1+2(Z(obs)e2)2)1/2], where Z(obs) > 0 is the nuclear charge observed at r --> infinity) condensation of electrons occurs on levels that have dropped from the upper continuum below the boundary omega < -m. The electric-field distribution is found in explicit form in both cases. For a bare charge Z0 of radius r0 < r(epsilon) the distribution corresponds to the asymptotically free regime: The charge Q(r) in a sphere of radius r[delV = Q(r)/r2] tends to zero as r --> r0 --> 0. With increase of the distance from the center, Q 2(r) increases and reaches its maximum value 1/2 at r approximately r(epsilon), and then falls to the value Z0 2e4/[1 + 2(Z0e2)2] at r approximately 1/m. Arguments are given that QED is logically closed as a theory with a point interaction with a consistent renormalization of the electron charge and with an electron mass of electromagnetic origin.

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IONIZA ON REAC ON OF P-N STRUCTURES IN INTEGRATED MICROCIRCUITS AT HIGH IONIZING-RADIA ON INTENSI ES

ANDREEV, SP; ASTVATSATURYAN, ER; GOLOVIN, AV; KUDRYASHOV, NA; KUCHERENKO, SS; POLUNIN, VA; CHICHERYUKIN, AV

SOVIET PHYSICS SEMICONDUCTORS-USSR; vol. 25; issue 1; pp. 75-78; year: 1991

Abstract: Analytic and numerical studies are reported of the effects of weak and strong ionizing radiation on p-n structures in integrated microcircuits. A quantitative criterion of the range of validity of a theory of the effects of weak ionizing radiation is found in the form of the ratio of the density of the minority carriers generated by irradiation to the dopant concentration. Calculations are made of the current-voltage characteristics of a semiconductor structure irradiated with strong ionizing radiation and a study is made of the recovery of a p-n junction after switching-on a specific negative bias voltage.

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RECORDING OF SMALL VIBRA ONS OF OBJECTS WITH THE USE OF INTRACAVITY DETEC ON OF THE 2-MODE GAS-LASER RADIA ON

ANissueHCHENKO, ML; ERMACHENKO, VM; GOLOVCHENKO, AM; KUROCHKIN, VY; NMOV, NV; PETROVSKII, VN; PROTSENKO, ED

KVANTOVAYA ELEKTRONIKA; vol. 18; issue 5; pp. 653-654; year: 1991

Abstract: Possible use of two-mode gas lasers for remote recording of small vibrations of objects has been studied. Vibrations of approximately 10(-3) lambda (lambda is the radiation wavelength) have been recorded at the distance of 3-5 m in the frequency range up to several megahertz. The maximal sensitivity of one of the suggested procedures for vibration recording has been evaluated.

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NATURAL INTENSITY FLUCTUA ONS IN SINGLE-MODE AND DOUBLE-MODE CO2-LASERS

ANissueHCHENKO, ML; ERMACHENKO, VM; GOLOVCHENKO, AM; KUROCHKIN, VY; NMOV, NV; PETROVSKII, VN; PROTSENKO, ED

KVANTOVAYA ELEKTRONIKA; vol. 18; issue 10; pp. 1176-1178; year: 1991

Abstract: Natural intensity fluctuations (NIF) have been studied in single-mode and double-mode CO2 lasers. The shape and level of NIF in them are determined. It is shown that the principal mechanism of the NIF formation is related with field fluctuation sources.

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CRI CAL CURRENT OF JOSEPHN LAT CE

BARANOV, MA; GORBACHEV, VS; SAVELEV, SE; CHERNOV, AS

FIZIKA NIZKIKH TEMPERATUR; vol. 17; issue 10; pp. 1267-1269; year: 1991

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FLUCTUA ONS ON NONEQUILIBRIUM DEFECTS AND SMEL NG OF IRRADIATED METAL

DEVYATKO, YN; ROGOZHKIN, SV

PissueMA V ZHURNAL TEKHNICHESKOI FIZIKI; vol. 17; issue 17; pp. 60-62; year: 1991

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EFFECT OF OXYGEN ATOM INTERAC ON ON THE OXIDA ON-KINE CS OF MAGNETS NEAR THE CURIE-POINT

DEVYATKO, YN; TRONIN, VN; TROYAN, VI

FIZIKA TVERDOGO TELA; vol. 33; issue 5; pp. 1479-1487; year: 1991

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MIRROR REFLEC ON OF QUANTUM AND PAR CLES FROM LID-STATE SURFACE

GORODNICHEV, EE; DUDAREV, SL; ROGOZKIN, DB; RYAZANOV, MI

ZHURNAL TEKHNICHESKOI FIZIKI; vol. 61; issue 6; pp. 210-212; year: 1991

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QUANTUM INTERFERENCE IN BACKSCATTERING OF CHARGED-PAR CLES BY DIRDERED MEDIUM IN MAGNE C-FIELD

GORODNICHEV, EE; ROGOZKIN, DB

ZHURNAL EKSPERIMENTALNOI I TEORETICHESKOI FIZIKI; vol. 100; issue 3; pp. 1009-1028; year: 1991

Abstract: The interference contribution to the angular spectrum of the charged particle backscattering by a 3D and 2D disordered systems in uniform magnetic field is calculated under a weak localization condition. Besides blunting of the spectrum peak due to breaking the coherence of the time-reversed waves it is shown that the spectrum asymmetry may be observed as well. In the case of magnetic field parallel to the medium surface the peak of the angular spectrum of the backscattered particles shifts with respect to the exact backward direction. The shift magnitude is governed by the average magnetic flux through the contour formed by the time-reversed trajectories of backscattered particles.

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THE EFFEC VE INTERPAR CLE SCREENING AND THE LOCAL-FIELD CORREC ON IN THE SPIN-POLARIZED ELECTRON-SYSTEM

Ivol.IEV, SV; BAKIN, VN

PHYSICA STATUS LIDI B-BASIC RESEARCH; vol. 164; issue 2; pp. 453-462; year: 1991

Abstract: The screening properties of a system of interacting spin-polarized electrons are investigated. The exact closed equation for the vertex function is received by a many-particle approach and the main contribution to that function is founded on the linear approximation of the generalized screened potential. The local field factor is calculated and its strong electron density dependence is demonstrated. The compressibility is positive in a wide interval of electron densities.

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NATURAL OSCILLA ON SPECTRA OF INTERAC NG ELECTRON-SYSTEM IN MUL LAYERED 2D-STRUCTURE

Ivol.IEV, SV; BAKIN, VN

FIZIKA TVERDOGO TELA; vol. 33; issue 11; pp. 3260-3266; year: 1991

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EFFEC VE-RANGE EXPANSION AND COULOMB RENORMALIZA ON IN THE ALPHA ALPHA, DT, AND DHE-3 SYSTEMS

KARNAKOV, BM; MUR, VD; POZDNYAKOV, SG; POPOV, VS

JETP LETTERS; vol. 54; issue 3; pp. 127-131; year: 1991

Abstract: An expression for the effective range derived here generalizes the Smorodinskii formula to the case of potentials with a Coulomb repulsion and an arbitrary angular momentum l. With increasing charges of the particles, there is an exponential renormalization of the low-energy parameters. These parameters are extracted from experimental data for the dt,dHe-3, and alpha-alpha-systems.

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POLES AND RENANCES IN LOW-ENERGY SCATTERING OF CHARGED-PAR CLES

KARNAKOV, BM; MUR, VD; POZDNYAKOV, SG; POPOV, VS

SOVIET JOURNAL OF NUCLEAR PHYSICS-USSR; vol. 54; issue 2; pp. 241-243; year: 1991

Abstract: The scattering length and effective range are determined for the system d He-3, and the positions of the poles of the scattering amplitude in the k plane are calculated. Bounds are obtained for the Coulomb renormalization of the low-energy parameters.

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GENERALIZATION OF THE GAMOW FORMULA TO THE MULTIDIMENSIONAL CASE

MUR, VD; POPOV, VS; SERGEEV, AV

SOVIET JOURNAL OF NUCLEAR PHYSICS-USSR; vol. 54; issue 4; pp. 575-581; year: 1991

Abstract: A generalization of the Gamow formula for the width GAMMA of a quasistationary level (with energy E = E(r) - i-GAMMA/2) is given for the case of multidimensional systems with separable variables. The condition for applicability of this approximation is obtained, and some examples are considered.

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ON THE NUCLEON DECAY OF SUBBARRIER SINGLE-PAR CLE STATES IN FT SPHERICAL NUCLEI

MURAVIEV, SE; URIN, MH

PHYSICS LETTERS B; vol. 262; issue 2-3; pp. 185-188; year: 1991

Abstract: The nucleon decay of subbarrier single-particle states with large angular momentum and parity opposite to that of the shell in soft spherical nuclei is considered. It is shown that the reduced probabilities of the nucleon decay into the ground state (0+) and into the first excited (2+) state of the daughter nucleus have qualitatively different energy dependences.

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QUANTIZATION RULES WITH ALLOWANCE FOR BARRIER PENETRATION

POPOV, VS; MUR, VD; SERGEEV, AV

ZHURNAL EKSPERIMENTALNOI I TEORETICHESKOI FIZIKI; vol. 100; issue 1; pp. 20-44; year: 1991

Abstract: A correction to the quasiclassical quantization rules is found which is connected with the taking into account of the barrier penetration. The equation derived defines both the position E(r) and width GAMMA of the quasistationary level. The results are compared with numerical solutions of the Schrodinger equation and with the exactly soluble models. A generalization of the Gamov formula for systems with separated variables is obtained. The possibility of extending the results to the relativistic case is discussed.

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QUANTIZATION RULES FOR QUASI-STATIONARY STATES

POPOV, VS; MUR, VD; SERGEEV, AV

PHYSICS LETTERS A; vol. 157; issue 4-5; pp. 185-191; year: 1991

Abstract: The modification of the Bohr-Sommerfeld quantization rules, which is due to the barrier penetrability, is found. The equation obtained is valid for an arbitrary analytical potential U(x), obeying the quasiclassical conditions. It determines both the position E(r) and the width-GAMMA of the quasistationary state. A generalization of the Gamow formula for multidimensional systems with separable coordinates is derived. A comparison with exactly solvable models as well as with numerical solutions of the Schrodinger equation for the Stark problem is performed.

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GENERALIZATION OF THE GAMOW FORMULA TO THE MUL DIMENSIONAL CASE

POPOV, VS; MUR, VD; SERGEV, AV

JETP LETTERS; vol. 53; issue 9; pp. 455-458; year: 1991

Abstract: The Gamow formula for a level width is generalized to the case of multidimensional systems with separable variables. A condition for the applicability of this approximation is found.

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The Propagation of Laser Radiation in a Stratified Turbid Medium in the Case of an Oblique incidence of the Broad Stationary Beam

Remizovich, VS; Shekhmametyev, SA

LASER PHYSICS; vol. 1; issue 2; pp. 172-179; year: 1991

Abstract: The problem of the propagation of the broad stationary beam of incoherent laser radiation in a stratified turbid medium with a strongly anisotropic scattering and strong absorption is considered. Analytical relations between the parameters of the scattered radiation, namely, the dispersion of the angular distribution, the polar angle, corresponding to maximum intensity, additional attenuation of the radiation flow are obtained in the diffusion approximation. The case of the two-layer medium, as well as the frequently encountered case of the medium demonstrating special stratification of optical parameters, when the ratio of photon angular diffusion to the extinction coefficient is constant, are analyzed in detail. A simple analytical expression for the radiation intensity as a function of depth, the polar and azimuthal angles, the optical properties of the medium and the angle of incidence is derived.

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ON THE INTENSITY OF WEAK AND E1 TRANSITIONS BETWEEN COMPOUND STATES OF NUCLEI

URIN, MH; VYAZANKIN, ON

PHYSICS LETTERS B; vol. 269; issue 1-2; pp. 13; year: 1991;

Abstract: A quantitative interpretation is proposed of the intensity of low-energy weak and E1 transitions between compound states of nuclei. It is shown that the contribution of the valence mechanism to these intensities is negligibly small compared to that of the temperature mechanism. The semiempirical approach to the description of the temperature mechanism has enabled us to establish a relation between the intensities of weak and E1 transitions and, on its basis, to interpret the corresponding experimental data.

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MEAN FREE-PATH OF PION AND NUCLEON QUASI-PAR CLES IN A HOT DENSE NUCLEAR MEDIUM

VOSKRESENSKII, DN; SENATOROV, AV

SOVIET JOURNAL OF NUCLEAR PHYSICS-USSR; vol. 53; issue 6; pp. 935; year: 1991;

Abstract: The mean free paths of nucleon and pion quasiparticles in a hot dense nuclear medium are calculated, taking into account the total amplitude of the NN interaction. The softening of the pion degree of freedom with density leads to a significant decrease in the mean free paths of the particles. The results support the application of the model of an expanding nuclear fireball to nucleus-nucleus collisions.

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