Faculty of Physics
M.V.Lomonosov Moscow State University
Menu
Theoretical and mathematical physics

## Brownian motion in weakly nonlinear systems induced by Gaussian fluctuations with arbitrary correlation time

### T.I. Lakoba

Moscow University Physics Bulletin 1992. 47. N 4. P. 1

A method is proposed for constructing a closed approximate equation for weakly nonlinear systems exposed to Gaussian noise with the correlation function of an arbitrary form.

Show Abstract
Radiophysics

## The region of applicability of the modified method of traveling waves in free space

### V.D. Gusev, S.M. Golynskii

Moscow University Physics Bulletin 1992. 47. N 4. P. 6

The region of applicability of the modified method of traveling waves in free space behind a chaotic phase screen is investigated. The model of normal fluctuations of the scattered field phase on the screen is considered in the smallangle scattering approximation. A criterion for the applicability of the modified method is obtained, which substantially extends the potentialities of using the ray interpretation of the wave field in free space as compared to the standard definition of the geometrical optics zone.

Show Abstract

## Cylindrical ferroelectric resonators with plane-parallel end-face electrodes

### G.V. Belokopytov, T.V. Krasyuk

Moscow University Physics Bulletin 1992. 47. N 4. P. 11

The problem of determining the eigenfrequencies of a cylindrical high-permittivity dielectric resonator is reduced to the solution of a transcendental equation of the zeroth approximation and subsequent calculation of corrections.

Show Abstract

## Nonstationary self-consistent model of autoelectronic emission from a metal cathode

### B.A. Markov, A.D. Poezd

Moscow University Physics Bulletin 1992. 47. N 4. P. 15

A model of autoelectronic emission for self-consistent nonlinear problems of heavy-current microwave electronics is discussed. On the basis of modeling of a complete nonstationary system of Maxwell-Vlasov equations it is shown that the injection current has a clearly pronounced pulsed character.

Show Abstract

## Relativistic gyrotrons with beam oscillatory velocity pumping in the interaction space by a nonadiabatic magnetic undulator

### A.F. Aleksandrov, V.A. Kubarev, V.A. Cherepenin

Moscow University Physics Bulletin 1992. 47. N 4. P. 19

A gyrotron construction is proposed in which the region of formation of a helical electron beam and the region of interaction are made eoincident. The pumping can be performed by magnetic undulators with a nonadiabatic (over the length} switching-on of the field. The question of the attainable efficiency of this type of devices is investigated for various injector voltages.

Show Abstract
Optics and spectroscopy

## Propagation and compression of pulses in media with dispersion losses

### Yu.E. D'yakov

Moscow University Physics Bulletin 1992. 47. N 4. P. 25

The spectral and temporal behavior of pulses propagating in selectively absorbing and amplifying media has been described. Optimization of pulse shape, compensation for dispersional distortions, and some new methods of compression based on dispersion losses are discussed. The evolution of the Gaussian FM pulse in a "parabolic" medium showing a square complex dispersion characteristic has been considered in detail, in particular, in a laser SRS amplifier. General estimates have been obtained for the energy in the "wings" of the pulse or its frequency spectrum.

Show Abstract

## Spectral characteristics of thin-layer interference filters

### A.V. Kosar', A.V. Kozlov

Moscow University Physics Bulletin 1992. 47. N 4. P. 35

A theoretical study has been carried out of the spectral characteristics (the wavelength dependence of radiant transmittance) of thin-layer interference filters (the total optical density of the structure is smaller than half a wavelength). Simple analytical expressions have been obtained that enable one to adequately determine the position and depths of all the extrema on the spectral characteristics of these interference filters. The specific features of the structures under consideration and the potentialities for their utilization in applied optics have been studied and discussed. The computer-aided numerical analysis confirmed the theoretical predictions.

Show Abstract

## Resonance excitation of surface electromagnetic waves on diffraction gratings in the IR region: anomalies of absorption and reflection

### A.A. Karabutov, I.A. Kudinov, V.T. Platonenko, M.A. Sogoyan

Moscow University Physics Bulletin 1992. 47. N 4. P. 40

Absorption of the IR radiation by metallic diffraction gratings was studied by using the optoacouatic effect. Narrow peaks that correspond to resonance excitation of surface electromagnetic waves (SEW) were discovered. The dependence of peak widths was investigated as a function of the SEW pathlength and the width of the angular spectrum of radiation. The macroscopic redistribution of radiation intensity was discovered experimentally in the beam specularly reflected from the grating.

Show Abstract

## The use of laser saturation fluorometry for the study of mechanisms of chlorophyll a fluorescence build-up in phytoplankton under conditions of mineral nutrition shortage

### M.Yu. Gorbunov, V.V. Fadeev, A.M. Chekalyuk

Moscow University Physics Bulletin 1992. 47. N 4. P. 47

The increase in the intensity of chlorophyll a fluorescence of phytoplankton under conditions of shortage of mineral nutrition was found to have two components. The first component, whose relative contribution to the overall process of fluorescence intensity change makes up 60-75%, is of a recombination origin and is due to a disruption of the electron transport between the intermediate acceptor Pheo and the primary quinone acceptor $Q_A$ in the reaction center of photosystem II (PS II). The second, nonrecombination, component is due either to weakening of the bond between the light-harvesting antenna and the PS II reaction center, or to disruption of the electron transport between the primary donor P680 and Pheo. It is shown that shortage of mineral nutrition results in the formation of certain number of nonreactive PS II reaction centers with disrupted electron transport from $Q_A$ to the secondary quinone acceptor $Q_B$.

Show Abstract

## Probability description of delayed fluorescence in higher plants for the model of the reaction center complex of photosystem II

### A.K. Kukushkin, V.A. Ryabov, E.A. Soldatova

Moscow University Physics Bulletin 1992. 47. N 4. P. 54

The probability method was used to describe delayed fluorescence of higher plants. The simplest model proposed is based on the notion of a complex of reaction centers in photosystem Il in which exposure to light induces separation of charges. The model includes pigments, donors and acceptors of electrons with a disrupted electron transport chain, with and without consideration for the nonradiative transition. The results obtained show that a multiexponential decay and a nonmonotonic kinetics of delayed fluorescence may arise in the course of back reactions occurring at the initial stages of electron transfer.

Show Abstract

## Stimulated Raman backscattering of the Gaussian pumping pulse: numerical experiment

### S.Yu. Nikitin, D.A. Sivashov

Moscow University Physics Bulletin 1992. 47. N 4. P. 60

In this paper we have studied the dynamics of stimulated Raman backscattering (SRBS) of the Gaussian pumping pulse in the plane wave approximation and without allowance for local nonstationarity. Three basic dynamic regimes have been revealed: quasistatic, modulation (spiking), and SRBS regime in an unbounded medium. The conditions for realization and the principal characteristics of these regimes have been established.

Show Abstract
Solid state physics

## Staebler-Wronski effect in amorphous hydrogenated p-type silicon films

### A.G. Kazanskii

Moscow University Physics Bulletin 1992. 47. N 4. P. 65

Illumination-induced variations of dark conductivity in amorphous hydrogenated silicon films ($\alpha$-Si:Н) doped with boron at different concentrations were investigated. Measurements were carried out in the 270 to 470 K temperature range. Three processes leading to conductivity variation were revealed. Two of them cause an increase in conductivity and are related to the film surface. The third process occurs in the bulk. The possible mechanisms of these processes are considered.

Show Abstract
Astronomy

## A multichannel detector of low-frequency GW-bursts based on laser deformograph

### A.V. Gusev, V.K. Kravchuk

Moscow University Physics Bulletin 1992. 47. N 4. P. 72

The possibility of using a laser deformograph as a detector of low-frequency GW-bursts in active filtering of seismic interferences under conditions of incomplete a priori information is considered.

Show Abstract
Theoretical and mathematical physics

## On the contribution of the vector component of torsion to the effect of interaction of polarized photons

### I.V. Yakushin

Moscow University Physics Bulletin 1992. 47. N 4. P. 76

It is shown that the purely vector part of torsion in the first-order perturbation theory with respect to the constant of interaction between the torsional and electromagnetic fields gives no contribution to the effect ·of interaction of polarized photons in the vapor of sodium atoms.

Show Abstract
Radiophysics

## The influence of thermal motion of electrons on a strongly nonlinear Langmuir wave

### I.M. Aleshin

Moscow University Physics Bulletin 1992. 47. N 4. P. 78

The stationary nonlinear Langmuir wave is investigated by the method of kinetic equation. The Maxwellian distribution is employed as the initial velocity distribution of electrons. The asymptotic Laplace method is used to find the nonlinear current. In contrast to the "water bag" type distribution, the limitation on the wave field amplitude is removed.

Show Abstract
Optics and spectroscopy

## Study of the dependence of the transition energy $E_1+\Delta_1$, on the $Hg_{1-x}Mn_xTe$ composition by the electrorefiectance method

### L.P. Avakyants, E.I. Veliyulin, A.A. Mamedov, A.V. Chervyakov

Moscow University Physics Bulletin 1992. 47. N 4. P. 81

Electroreflectance spectra of $Hg_{1-x}Mn_xTe$ solid solutions were used to determine the coefficients of a polynomial that expresses the dependence of the transition energy $E_1+\Delta_1$ on the concentration parameter $x$. The possibility of local topographic investigations of the composition heterogeneity on the semiconductor surface is demonstrated.

Show Abstract
Geophysics

## A study of nonlinearity in the process of tsunami generation by sea floor motion

### 0.V. Kostitsyna, M.A. Nosov, N.K. Shelkovnikov

Moscow University Physics Bulletin 1992. 47. N 4. P. 83

The process of tsunami wave generation by motions of the sea floor with residual displacement has been investigated by numerical modeling. Fast, medium-velocity, and slow floor oscillations are considered. The role of nonlinear effects is estimated as a function of the magnitude of the sea floor displacement and oscillation duration in the cases of elevation and subsidence of a sea floor section. The experimental data are compared with the results of numerical experiments.

Show Abstract
Solid state physics

## Pyroelectric coefficient of the PZT-40 ceramics in the 1.5-80 K temperature range

### A.B. Esengaliev, V.K. Novik, V.V. Novikov, A.G. Segalla

Moscow University Physics Bulletin 1992. 47. N 4. P. 87

The pyroelectric coefficient was measured in the 1.5-80 K temperature range and the permittivity in the 1.5-250 K range for PZT-40 ferroelectric ceramics.

Show Abstract