Faculty of Physics
M.V.Lomonosov Moscow State University

## Theory of the anomalous skin effect in a plasma pinch with a gradually falling-off electron concentration

### A.N. Vasil'ev

Moscow University Physics Bulletin 1979. 34. N 1. P. 1

The interaction of cylindrical electromagnetic waves in a plasma pinch is examined in the limiting case of strong anomalous skin effect. We obtain the integrodifferential equations describing a cylindrical pinch. Particular attention is paid to the examination of an electron concentration which falls off gradually with increasing distance from the axis of the pinch. We solve exactly an integrodifferential equation with a kernel, which does not reduce to the difference type. By use of a Mellin transform the integrodifferential equation reduces to a functional equation whose solution can be obtained in general form. We examine separately the absorption of waves of the electric and magnetic types. We obtain the coefficients of reflection from the pinch for each type of wave and the linear resistance of the plasma pinch.

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## Interference of a wave train of finite length in a fabryperot interferometer

### M.A. Khashchan

Moscow University Physics Bulletin 1979. 34. N 1. P. 11

The spectral compositon of radiation is correlated with the length of a train of waves for evaluating the relative widening and decrease in visibility of the pass band of a Fabry - Perot interferometer. The degree of monochromaticity of the light is expressed through the number of coherent waves, which is determined by the ratio of the coherence length to the path difference in the interferometer. Inasmuch as this number tends to infinity for null path differences, the degree of monochromaticity is relative. We derive analytic formulas which describe the widening of the bands with increasing path difference. We give a relation between the half - widths of the apparatus, spectral, and observable functions. We examine the workings of interference mirrors and filters of light for the case of quasimonochromatic radiation.

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## The amplitude structure of the sound pressure field and the vibrational velocity close to a liquid sphere when a plane wave is incident on it

### N.S. Vinogradov, S.F. Nekrich, F.V. Rozhin and 0.S. Tonakanov

Moscow University Physics Bulletin 1979. 34. N 1. P. 19

The near field of the sound pressure and the components of the vibrational velocity when a plane wave is incident on a liquid sphere is calculated. The dependence of the field on the angles of incidence of the plane wave, the distance from the surface of the sphere, the wave dimensions of the sphere, and the frequency of the incident wave are analyzed. Different cases of the ratio of the velocities of propagation of the sound in the medium and in the material of the sphere for the same densities of the medium and the sphere are considered. It is shown that for specified wave dimensions of the sphere is a region where the amplitude characteristics of the field change sharply depending on the ratio of the wave impedances of the medium and the material of the sphere.

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## Investigation of the processes connected with the transfer of an electron in the chlorolayers of higher plants by the method of thermoluminescence

### A.T. Chernokolev (Bulgaria), A.K. Kulushkin, and M.K. Solntsev

Moscow University Physics Bulletin 1979. 34. N 1. P. 27

Five thermoluninescence peaks in the chlorolayers of higher plants were detected with temperatures of the maxima (T_$M$) of -l65°C, -10°C, +25°C and +55°C. The spectral characteristics of the first three peaks were obtained. The dependence of the intensity of the thermoluminescence of the peaks with (T_$M$) equal to -10°C and +25°C on the temperature of the radiation was established. The effect of different additions (diuron, DCPIP, mixtures of DCPIP with ascorbate and mixtures of ferricyanide and ferrocyanide) which act on the chain of the electron transfer between two photosystems, on the characteristics of the thermoluminescence of the peaks (T_$M$) equal to -10°C and + 25°C are investigated. The results of the experiments are interpreted within the framework of the hypothesis which explains the thermoluminescence as due to the reverse transfer of electrons from restored carriers in the chain of electron transport between two photosystems.

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## Phase and angle fluctuations in radiowave scattering from an ionospheric layer

### V.D. Gusev and N.A. Makhmutov

Moscow University Physics Bulletin 1979. 34. N 1. P. 33

We investigate the scattering of radio waves in reflection from an ionospheric layer with random inhomogeneities of the electron concentration. It is assumed that the average shape of the layer is described by a parabolic model, and that the inhomogeneities have a Gaussian correlation function. The problem is solved by approximation of geometrical optics. It is well known that, within the framework of this approximation, the amplitude modulations of the field are negligibly small compared to those of the phase. Thus the fluctuations of the phase and its spatial derivatives (the direction cosines of the beam) are the fundamental characteristics of an ionospherically scattered field. In this paper we obtain analytical expressions for the dispersion of these quantities for both normal and oblique reflections. These expressions go over at low frequencies to the well known formulas for a linear layer, while differing appreciably from them at frequencies close to the maximum usable frequency.

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## Open electrodynamic systems in relativistic diffraction electronics

### V.I. Kanavets, N.F. Ryapolov, A. N. Sandalov and V.A. Cherepenin

Moscow University Physics Bulletin 1979. 34. N 1. P. 40

We examine the possibility of using an open diaphragmed transmission line as an electrodynamic system of relativistic diffraction electronics. We investigate theoretically and experimentally the amplitude and phase characteristics of the line used as a homogeneous and inhomogeneous wave guide. The theoretical investigation was done by numerical solution of nonlinear integral equations by iteration methods. We describe a method of measuring the phase shift of a wave on its passage through the diaphragms. The experimental research was done in the millimeter - wave - length region. Good agreement was obtained between the theoretical and experimental results. The theoretically calculated efficiency for the diffraction radiation of a relativistic polyhelicoid current in the investigated wave guide reaches 25 to 30%.

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## Scattering of coherent radiation by an oscillating diffuse reflector

### V.S. Anchutkin and V.I. Shmal'gauzen

Moscow University Physics Bulletin 1979. 34. N 1. P. 49

We consider theoretically the scattering of coherent radiation by a rough surface that is subjected to small perturbations in the form of transverse traveling or standing waves. It is shown for a special geometry of the illumination of the diffuse scatterer in the form of two spots, that the intensity distribution in the observation plane constitutes a characteristic "spotted" picture modulated by a system of Young's interference fringes. The presence of the perturbation leads to vibrational motion of the fringe system. This phenomenon can be used to observe and study vibrations of rough surfaces.

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## Wave reflection from a triangular layer

### N.A. Makhmutov

Moscow University Physics Bulletin 1979. 34. N 1. P. 55

The reflection of waves from layers with a parabolic and triangular profile is of interest when investigating the ionospheric propagation of radio waves. Although the properties of a parabolic layer are fairly well known, the problem of the reflection of waves from a triangular layer has not been considered in the literature. In this paper, using the accurate solutions of the Helmholtz equation for a linear layer, we obtain analytical expressions for the complex reflection and transmission coefficient of a triangular layer which are expressed in terms of cylindrical functions of order 1/3. For frequencies considerably greater or less than the critical frequency these expressions give quantitative agreement with the well - known equations, but differ considerably from these relations at frequencies close to the critical frequency.

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## The form of the axial shadow for large displacements of a composite nucleus

### N.V. Eremin, G. Martinez (Cuba), Yu.V. Melikov, A.F. Tulinov, and N.G. Chechenin

Moscow University Physics Bulletin 1979. 34. N 1. P. 61

A model describing the form of the angular distributions of particles emitted from a single crystal in the direction of the crystallographic axes is developed. The interaction potential of the particles with the crystal was chosen in the form of the sum of the interaction potentials with neighboring chains, and therefore had an axially nonsymmetrical form. The effect of the lifetime of the composite nucleus on the shape of the angular distribution of the nuclear - reaction products is investigated with in the framework of this model. It is found that the form of the angular distribution depends both on the value of the displacem e n t during the lifetime of the composite nucleus and on the direction of the displacement of the composite nucleus from the lattice point of a lattice in a plane perpendicular to the specified crystallographic axis. In particular it is shown that for certain orientations and for large values of the displacements (υ⊥τ~0,1 nm) of the composite nucleus the minimum in the angular distribution of the particles and of the reaction products may turn into a maximum. In addition to this there are integral characteristics of the angular distributions which for high sensitivity to the value of the displacement depend slightly on the orientation of the displacement of the composite nucleus.

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## Scheme of 181^Ta levels excited in the (N/n'γ) reaction

### V.D. Avchukhov, M.R. Ahmed (Iraq), K.A. Baskova, Т.M. Bekukh, A.B. Vovk, L.I. Govor, and A.M. Demidov

Moscow University Physics Bulletin 1979. 34. N 1. P. 66

Измерен спектр Ƴ-лучей при неупругом рассеянии быстрых нейтронов реактора на 181^Та. Из спектра выделена 71 Ƴ-линия, из них 40 обнаружена впервые. Среди известных уровней 181^Та размещены лишь немногие из найденных нами Ƴ-переходов. Для размещения части' из впервые обнаруженных Ƴ-переходов введено 11 уровней следующих энергий: 886,4; 988,4; 1091,0; 1349,2; 1381,2; 1432,9; 1616,5; 1636,7; 1643,3; 1746,1 и 1769,4 кэВ. Обнаружено отклонение экспериментальных величин заселяемостей низколежащих уровней 181^Та от значений, вычисленных с помощью статистической модели.

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## Excitation of a periodic structure in an open resonator

### D.G. Afoniri and A.I. Kostienko

Moscow University Physics Bulletin 1979. 34. N 1. P. 74

The dispersion characteristics of hemispherical resonators with a plane mirror covered with a periodic structure of the "comb" type and low-Q open systems consisting of a radiating antenna of the "horn" type and a plane mirror with a periodic structure are investigated experimentally. Effective interaction between an electron beam close to the periodic structure with the harmonics (up to the tenth) of the diffraction mode and also with higher harmonics in the traveling-wave modes are found.

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## Some characteristics of the waveguide mode of a gas laser

### D.A. Kozyrev and P.V. Korolenko

Moscow University Physics Bulletin 1979. 34. N 1. P. 78

The efficiency of the feedback provided by the external mirrors of the resonator for a He-Ne waveguide laser at a wavelength of 3.39 μm is investigated experimentally. The experimental data obtained are compared with the results of theoretical calculations and show good agreement. The spatial distribution of the field of the modes of oscillation generated by the laser are investigated for different parameters of the resonators and gas-discharge tubes. It is established that tuning of the laser mirrors leads to complication of the mode composition of the emission. The dependence of the gain margin on the degree of detuning of the laser mirrors is measured.

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## Magnetic characteristics of highly dispersed iron

### O.S. Galkina, L.V. Lazareva, Т.M. Shvets and A.S. Shitova

Moscow University Physics Bulletin 1979. 34. N 1. P. 82

The results of an experimental investigation of the concentrational dependence of magnetic characteristics of the form K=f(C)and K=f(Cm), where К is the measured magnetic parameter, С is the concentration of powder in the specimen, and Cm is the iron particle packing density in the specimen, are given. The electrochemical method employed to obtain highly dispersed iron enabled us, by varying the electrochemical electrolysis mode, to obtain powders with different concentrations of the magnetic phase Cm in them. It is shown that all the fundamental magnetic characteristics (the saturation magnetization Is, the remanence Ir, the shape of the hysteresis loop, and the coercive force) depend both on the concentration of the magnetic phase in the initial specimens Сm, and on the particle packing density in the specimen Cm.

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## Correlation function of spatial fluctuations of light scattered by the nematic phase of a liquid crystal

### S.V. Kir'yanov

Moscow University Physics Bulletin 1979. 34. N 1. P. 87

We calculate the correlation function for fluctuations of the electrical component of a light field which is scattered by fluctuations in the orientation of the molecules in a nematic liquid crystal (NLC). It is shown that taking into account the fluctuations of the complete orientation tensor Sij leads to the occurrence of elements in the correlation matrix of the scattered field which cannot be obtained from examining the scattering of light from the director fluctuations in an NLC. We compare the correlation matrices of the fluctuations of the scattered field in an NLC and an isotropic liquid crystal (ILC). It is established that the correlation matrix of the scattered field changes strongly on transition from scattering light in the isotropic phase of the LC to scattering in the nematic phase.

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## The effect of the interaction of acoustic waves in layered media

### E.P. Lanina

Moscow University Physics Bulletin 1979. 34. N 1. P. 91

Parametric interaction between acoustic waves in layered periodic nonlinear media is considered. The conditions for synchronism between the signal wave and the pumping wave is investigated using numerical methods. Parametric interaction between the waves in a plexiglass - water periodic structure was observed experimentally. The local gain and the suppression of the signal were measured.

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## Periodic density distribution function of nonequilibrium charge carriers in an inhomogeneously illuminated semiconductor

### A.F. Rumynina

Moscow University Physics Bulletin 1979. 34. N 1. P. 95

We examine several features of a spatially inhomogeneous nonequilibrium system with interband absorption of light. The fluctuational stability of such a system is also established.

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