Faculty of Physics
M.V. Lomonosov Moscow State University

# Issue 5, 1992

## The theory of transversely inhomogeneous heavy-current beam-plasma amplifier under conditions of collective Cerenkov effect

### M.V. Kuzelev, V.A. Panin

Moscow University Physics Bulletin 1992. 47. N 5. P. 1

The paper is concerned with both linear and nonlinear theories of amplifying electromagnetic plasma waves in a transversely inhomogeneous beam-plasma system of a general form under conditions of the collective Cerenkov effect. The optimum length and efficiency of amplification, as well as the output electromagnetic radiation power have been calculated analytically and numerically.

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## The effect of transverse inhomogeneity of the pumping field on electron motion in nonadiabatic magnetic undulators with guiding magnetic field

### V.A. Kubarev

Moscow University Physics Bulletin 1992. 47. N 5. P. 8

Setting up optimal radiation regimes of helical relativistic electron beams requires a definite value of the electron pitch factor. The presence of a transverse inhomogeneity of the pumping field in real undulators leads to the following two main consequences: a widening of the nonlinear resonance and a drift of the guiding centers of the particles. A theory of these effects is developed for symmetric and asymmetric undulators with a homogeneous guiding magnetic field.

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## Characteristics of intermode striction coupling in spherical electroacoustic resonators

### G.V. Belokopytov, N.P. Pushechkin, V.N. Semenenko

Moscow University Physics Bulletin 1992. 47. N 5. P. 16

Integrated characteristics of the intermode striction interaction of electromagnetic and acoustic oscillations in spherical resonators have been studied. Selection rules are established and integrated striction interaction characteristics are calculated with consideration for the vector character of the fields and the electrostriction tensor anisotropy. There was good agreement between the calculated and experimental data on striction parametric excitation of radial elastic oscillations by UHF pumping in potassium tantalate dielectric resonators.

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## Polarization effects in light propagation through an acoustic field in an isotropic medium

### A.I. Balakshii, D.A. Khasan

Moscow University Physics Bulletin 1992. 47. N 5. P. 22

The variation of light polarization in the process of Bragg's acoustooptic interaction has been investigated theoretically. It is shown that in the propagation of linearly polarized light through an acoustic field excited in an isotropic medium the light radiation becomes elliptically polarized. By varying the ultrasound intensity or frequency it is possible to control the polarization state. The effect of polarization nonreciprocity has also been studied for two light waves propagating through an acoustic field in the opposite directions.

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Optics and spectroscopy

## The effect of variation of the refractive index and thickness of layers in thin-layer interference filters on their optical parameters

### A.V. Kosar', E.V. Putrina

Moscow University Physics Bulletin 1992. 47. N 5. P. 28

Changes in the refractive index of a medium to be matched and in the matching wavelength upon variation of the refractive indices and thicknesses of layers in thin-layer interference filters (TIF) were studied theoretically (the optical thickness of the layers is smaller than a quarter wavelength) for TIF with two and three layers in a period. New properties of such filters were discovered, in particular, the invariance of these changes with respect to the number of periods when the refractive indices of the layers vary. Simple analytical expressions were obtained that allow an adequate determination of the shift in the parameters under consideration. A computer-aided numerical analysis confirmed the theoretical predictions.

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## Fluorescence saturation phenomenon for dissolved organic compound

### S.V. Patsaeva, V.V. Fadeev, E.M. Filippova, V.V. Chubarov, V.I. Yuzhakov

Moscow University Physics Bulletin 1992. 47. N 5. P. 35

Specific features of the effect of fluorescence saturation for an organic compound dissolved in water were studied after fluorescence was excited by an LGI-505 nitrogen laser ($\lambda = 337$ nm, $\tau = 8$ ns, photon flux density $F = 10^{26}$ cm$^{-2}$ $s^{-1}$). The experimental data obtained are discussed in terms of the model concepts of the origin of the fluorescence band for the dissolved natural organic compound.

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## Concentration dependence of spectral and luminescence features for solutions of pyrazoline dyes

### 0.Yu. Rodionova, S.N. Shcherbo, V.I. Yuzhakov

Moscow University Physics Bulletin 1992. 47. N 5. P. 39

A study on the concentration dependence of spectral and luminescence properties of Luminophor 59 solutions in toluene, dioxane, dimethylformamide, and ethanol has shown that this dye forms associates at concentrations greater than $10^{-5}$ mole/liter. This conclusion has been supported by the data on the luminescence parameters. The quantum yields and lifetimes of fluorescence have been determined for the dye studied.

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## Algorithms for multiparameter reconstruction of spectral and luminescence characteristics by the fluorescence saturation method

### N.Ya. Serov, V.V. Fadeev, A.M. Chekalyuk

Moscow University Physics Bulletin 1992. 47. N 5. P. 44

Considered is the possibility of using fluorescence saturation curves to find the following molecular parameters: (i) the quantum yield of triplet states, (ii) the lifetime of the first excited singlet state $S_1$, and (iii) the absorption cross section for a transition from the ground state to $S_1$ at the wavelength of excitation. Algorithms for a simultaneous determination of two and three parameters have been proposed. Requirements to the accuracy of saturation curve measurements were found by mathematical modeling. The results of an experimental check-up of the proposed solution algorithm for a three-parameter problem are presented for the case of eosine aqueous solution.

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Acoustics and molecular physics

## Geophysical factors of asymmetry origination in precursors of biological systems

### V.A. Tverdislov, M.R. Kuznetsova, L.V. Yakovenko

Moscow University Physics Bulletin 1992. 47. N 5. P. 51

A hypothesis is formulated which holds that breaking of symmetry in nature occurred in the prebiological evolution stage at the nonequilibrium ocean-atmosphere interface, and origination of aerosols from the ocean surface layer with inverted composition predetermined subsequent biological evolution.

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Geophysics

## Investigations of velocity field in flows of complex structure

### E.P. Anisimova, V.V. Petrov, A.A. Speranskaya, M.V. Shitov

Moscow University Physics Bulletin 1992. 47. N 5. P. 57

The hydrogen bubble method is used to study the structure of a flow of dense liquid moving in a quiescent liquid of a lower density. It is shown that in the mixing layer with stratified density distribution the velocity profile can be calculated by the Prandtl formula provided the effect of the density field on the velocity is taken into account.

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Astronomy

## Z parameters of a piezoelectric transducer for solid-state gravitational antennas

### A.V. Gusev, A.V. Tsyganov

Moscow University Physics Bulletin 1992. 47. N 5. P. 62

A system of $Z$ coefficients is computed for a piezoelectric transducer as a minor shift generator of a Weber-type solid-state gravitational antenna.

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Solid state physics

## The effect of semiconductor-metal phase transition on the hydrate layer on vanadium dioxide films

### A.V. Zoteev, N.L. Levshin, S.Yu. Poroikov

Moscow University Physics Bulletin 1992. 47. N 5. P. 65

The influence of the semiconductor-metal phase transition on the hydration and dehydration processes in polycrystalline vanadium dioxide fihns has been studied by electrophysical and mass-spectroscopic methods. An enhanced desorption capacity and accelerated adsorption-desorption processes were observed in the temperature region corresponding to the phase transition and also in the vanadium dioxide metal phase.

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Atomic and nuclear physics

## Modeling and analysis of the energy spectra of $\delta$ electrons generated by ultrarelativistic hadrons

### B.I. Goryachev, N.V. Lin'kova

Moscow University Physics Bulletin 1992. 47. N 5. P. 70

The authors present the results of mathematical modeling of an experiment designed to determine the parameters of the electromagnetic structure of hadrons by analyzing the energy spectra of $\delta$ electrons generated by the hadrons.

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## Diffraction by dielectric discontinuities in a partially dielectric-filled below-cutoff waveguide

### V.V. Gruzdev, V.P. Modenov, Yu.A. Pirogov, E.E. Fominova

Moscow University Physics Bulletin 1992. 47. N 5. P. 74

Diffraction of the wave $H_{10}$ by the below-cutoff section of a partially dielectric-filled waveguide has been considered. The problem is solved in an exact electrodynamic statement. Mathematical modeling is done by the generalized scattering matrix method. Propagation constants are obtained by differentiation with respect to a parameter. The dependence of numerical modeling results on the number of modes is studied. The results of the numerical analysis and physical experiments are compared.

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## Visual observation of the spatial distribution of output radiation from a Cerenkov microwave oscillator based on relativistic electron beam

### A.F. Aleksandrov, S.Yu. Galuzo, A. M. Kuznetsov

Moscow University Physics Bulletin 1992. 47. N 5. P. 78

A procedure is described for observation of the spatial distribution of microwave radiation generated by a relativistic heavy-current pulsed Cerenkov-type oscillator. The technique uses the microwave breakdown in air occurring under low pressure in a thin-layer chamber formed by the surfaces of two dielectrics.

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Geophysics

## Dependence of the ion fractionation coefficient in sea aerosols on the rate of evaporation from the sea surface

### M.R. Kuznetsova, E.V. Karavaeva, V.A. Tverdislov

Moscow University Physics Bulletin 1992. 47. N 5. P. 82

It is shown that the difference between the chemical composition of sea aerosols and that of sea water may be due to irreversible processes of heat and mass exchange between the ocean and the atmosphere. These processes may cause changes in the chemical composition of the ocean surface microlayer, which generates aerosols.

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Solid state physics

## A study of magnetic susceptibility of single-crystal gadolinium under all-round compression

### S.A. Nikitin, Yu.I. Spichkin, A.M. Tishin

Moscow University Physics Bulletin 1992. 47. N 5. P. 85

We measured the dependences of the initial magnetic susceptibility on the temperature $\chi(T)$ of a Gd single crystal along the $c$ and $b$ crystallographic axes in external magnetic fields and up to 1 GPa. The $\chi(T)$ curves were found to have maxima at the Curie temperature $\Theta_C$, the spin-reorientation transition temperature $\Theta_{SR}$, and the temperature $\Theta_A = 140$ К. The derivatives $\partial\Theta_C/\partial P$ and $\partial\Theta_{SR}/\partial P$ are determined, which are -13 and -67 K GPa$^{-1}$ along the $c$ axis and -12 and -29 K GPa$^{-1}$ along the $b$ axis, respectively.

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## On an additional component of spontaneous polarization of a $KH_2РO_4$ single crystal

### A.B. Esengaliev, V.K. Novik, V.N. Novikov, N.D. Gavrilova, N.P. Zaitseva, S.V. Bogatyreva

Moscow University Physics Bulletin 1992. 47. N 5. P. 89

The pyroelectric coefficient of a KDP (potassium dihydrophosphate) single crystal in nonpolar directions was measured. The data obtained suggest a possible mechanism underlying the appearance of an additional component of spontaneous polarization.

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