R e v i e w s

Optics and spectroscopy

Moscow University Physics Bulletin 1996. N 6. P. 1

А series of studies presented at the 1996 Lomonosov Lectures is described. The studies were devoted to ultra-fast nonlinear-optical diagnostics of laserinduced processes in the substance bulk and at the interface. They included the development of physical foundations and the organization of pioneering experiments with the aid of specially designed pulsed laser systems. The structurally sensitive techniques of nonlinear-optical time-resolved diagnostics, or spectrochronog1·aphy, developed in this research, have speeds of response in the range from units and tens of nanoseconds to tens and hundreds of femtoseconds.

Show AbstractRadiophysics

Moscow University Physics Bulletin 1996. N 6. P. 12

Phenomena that accompany focusing of powerful ultrasonic beams have been reviewed. А possibility to increase the radiation force and to contract the region of its localization in а nonlinear focusing operation has been shown. А method has been proposed to produce shock fronts in the focus due to the synthesis of а special initial profile which enaЫes the wave energy to Ье transported with almost no losses and to organize its local liberation in the focus bу "switching on" nonlinear absorption. А theory has been developed of а new higbly sensitive diagnostic method based upon remote excitation of low-frequency shear waves in soft biological tissues Ьу means of powerful modulated ultrasound.

Show AbstractMoscow University Physics Bulletin 1996. N 6. P. 25

The article is а review of publications on parametrically bound three-wave solitons in dispersive anisotropic media with quadratic nonlinearities. The character of cooperative self-action of plane monochromatic waves is studied. The properties of space and time solitons are discussed in the framework of quasi-optical diffraction theory and of the second approximation of linear dispersion theory with regard to the detuning of phase and group velocities. А simple model is considered of mutual focusing of beams and pulses in а medium with quadratic nonlinearity. BistaЫe solitons are analyzed for the case of interference between two channels of wave packet reactive interaction with an integer frequency ratio and in the presence of cuЬic nonlinearity. The evolution of extremely short pulses described in numerical experiments bу nonlinear Maxwell equations is traced. Experimental results of observation of optical solitons in crystals with quadratic nonlinearities are reported.

Show AbstractR e g u l a r p a p e r s

Theoretical and mathematical physics

Moscow University Physics Bulletin 1996. N 6. P. 42

The correct statement of proЪlems concerning the determination of parameters of а gas atmosphere in the process of cementation basing on indirect data, and the determination of the equilibrium constant in the interaction of an atmosphere with the metal surface for the same process has been proposed and justified. The algorithms of their solution have been developed and realized in Si-programs.

Show AbstractSolid state physics

Moscow University Physics Bulletin 1996. N 6. P. 48

It has been shown that the internal field of action in iron borate single crystals, as distinguished from the other known magnetic materials, is accelerating at the initial stage of pulsed magnetic reversal. When the main stage is completed, the field changes its sign, reaches the value of the external remagnetizing field, and oscillates about this value with а gradually decreasing amplitude. The oscillation amplitude reaches its maximum with the remagnetizing field strength corresponding to а magnetic reversal curve break.

Show AbstractMoscow University Physics Bulletin 1996. N 6. P. 51

Multilayer Fe/ Al films were synthesized Ьу cathode discharge sputtering with oscillating electrons. The Fe layers were about 6 А thick, the Al layers were 6 to 95 А thick, and the number of layers varied from 250 to 830. The behavior of Fe atoms in the superlattices was studied Ьу the methods of radiographic analysis, magnetic measurements of main magnetic characteristics, 57Fe Mossbauer spectroscopy, and magnetic phase analysis.

Show AbstractMoscow University Physics Bulletin 1996. N 6. P. 62

А frequency dependence has been found of the phonon contribution to а.с. hopping conductivity associated with transitions between impurity electronic states in а quantum well. It is shown that the transverse electric field may lead to а significant decrease in conductivity.

Show AbstractMoscow University Physics Bulletin 1996. N 6. P. 62

А new method has been proposed for the determination of the diffusion length and lifetime of minority carriers in wafers with p-n junctions. Nonequilibrium carriers are excited Ьу two light beams modulated Ьу а single frequency, one of which is absorbed heavily and the other one readily. The conditions of modulation of these beams are chosen such that the total а.с. voltage across the p-n junction vanishes. The diffusion length is determined from the ratio of light beam intensities and the lifetime is determined from the frequency dependence of this ratio or from the phase shift between the modulations. The numerical computations showed that the method can bе applied to silicon solar cells. The advantages of the method are discussed.

Show AbstractMoscow University Physics Bulletin 1996. N 6. P. 67

А phenomenological model of isomorphic phase transitions in thin ferroelectric films has been considered taking into account spatial inhomogeneity and size effects. The solution of the boundary value proЫem Ьу numerical methods enaЬled us to conclude that size effects and inhomogeneity of ferroelectrics do not suppress isomorphic phase transitions, whose observation in thin ferroelectric films is in principle possiЫe.

Show AbstractAstronomy

Moscow University Physics Bulletin 1996. N 6. P. 72

А comparison of the spectra of the day length and of the axial component of the atmospheric angular momentum reveals an appreciaЫe influence of atmospheric turbulence on the Earth's rotation. Day length variations with periods from several days to four months are determined Ьу turbulence. It has been shown that the periods of the majority of harmonics are close to the periods of natural atmospheric oscillations caused Ьу variations of the latitudinal temperature difference.

Show AbstractB r i e f r e p o r t s

Theoretical and mathematical physics

Moscow University Physics Bulletin 1996. N 6. P. 77

Scale relations that appear in applying the method of many-particle density functionals are considered. Scale transformation is applied to oЬtain the relations for the kinetic energy functionals and for the potential energy of interparticle interactions and for the interactions of particles with an external field for the ground states of the systems of charged particles in а pure Coulomb field. The Clausius virial theorem for the method of many-particle density functionals has been formulated.

Show AbstractRadiophysics

Moscow University Physics Bulletin 1996. N 6. P. 79

Тransformation of spectra of acoustic signals of N- and S- types, that contain several oscillations of pressure, in а nonlinear viscous medium for different laws of the field decay at the pulse tails is considered. Dynamics of spectra in the process of formation of Ьipolar pulses, described Ьу self-similar solutions of the linearized or complete Burgers equation, is observed.

Show AbstractSolid state physics

Moscow University Physics Bulletin 1996. N 6. P. 83

This paper describes the results of investigations of the magnetic and magnetooptical properties of Au/Co-wedge/ Au {001} sandwiches. It was found that the transverse Kerr effect (ТКЕ) undergoes oscillations with а change of the thickness of the Co-wedge from О to 20 А. It has been established that the period of these oscillations is Т 4-5 А. The value of Т has been found to depend on the quantum energy of incident light. It has been proved that the oscillations of the ТКЕ are caused bу quantum size effects.

Show AbstractGeophysics

Moscow University Physics Bulletin 1996. N 6. P. 86

Тransformations in the structure of bottom density current under the effect of vortex-wave processes are analyzed. Quasi-stationary, wave, and vortex components of the velocity profile are distinguished. А variance ratio for the internal wave in the suspension-stratified current is obtained. Vortex-like disturbances in the velocity are revealed. А procedure for analytical description of the flow velocity profile with allowance for the effect of vortex-wave processes is developed and tested Ьу using full scale measuring data.

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