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

## On consistency of the quantum and classical descriptions of a relativistic neutral particle with spin 1/2

### A.E. Lobanov, O.S. Pavlova

Moscow University Physics Bulletin 1999. 54. N 4. P. 1

An operator that makes it possible to include in the Dirac equation solution the interaction between the neutral particle anomalous magnetic moment and the electromagnetic fields, for which the Bargmann-Michel-Telegdi equation gives the spin evolution exact description, is constructed.

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## Excitation of a waveguide with complex filling

### A.N. Bogolyubov, A.L. Delitsyn, A.G. Sveshnikov

Moscow University Physics Bulletin 1999. 54. N 4. P. 6

Excitation of a waveguide with a complex dielectric and magnetic filling is examined. A new scheme for the method of normal waves is suggested.

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## Ultimate discrimination precision for the specified-energy states

### I.I. Kaledin, F.Ya. Khalili

Moscow University Physics Bulletin 1999. 54. N 4. P. 12

A problem of discriminating two quantum energy states is considered. It is shown that in this case the dynamic rigidity of the nondemolition energy measuring instrument does not affect the reliability of states discrimination.

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## The initial- and final-state interaction effects in the production of $\pi^{-}\Delta^{++}$ particles on a proton by real and virtual photons

### E.N. Golovach$^1$, V.S. Zamiralov$^1$, B.S. Ishkhanov$^1$, V.I. Mokeev$^1$, M.V. Osipenko$^1$, D.A. Rodionov$^1$, G.V. Fedotov$^1$, M. Battaglieri$^2$, A. Longhi$^2$, G. Ricco$^2$, M. Ripani$^2$, and M. Taiuti$^2$

Moscow University Physics Bulletin 1999. 54. N 4. P. 23

Absorption effects in the initial and final states of the reaction $\gamma p \rightarrow \pi^{-}\Delta^{++}$ involving real and virtual photons are analyzed. From the condition of the experimental data best fit, the absorption parameters are obtained.

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Atomic and nuclear physics

## Calculating the total high energy ion-atom scattering cross section in the eikonal approximation

### V.A. Bilyk$^1$, V.L. Shablov$^1$, and Yu.V. Popov$^2$

Moscow University Physics Bulletin 1999. 54. N 4. P. 17

A variant of the optical theorem application to calculating the total ion-atom scattering cross sections is proposed. Difficulties caused by an infinite zeroangle elastic scattering amplitude that arise in similar calculations in the eikonal approximation are eliminated by explicitly taking into account many-particle character of the scattering process.

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Optics and spectroscopy

## Concentration dependence of the fluorescence properties of oriented dye molecules in polymer films

### A.V. Grachev, V.I. Yuzhakov

Moscow University Physics Bulletin 1999. 54. N 4. P. 29

A relationship between the orientation degree of dye molecules in stretched polyvinyl alcohol films and the concentration of these molecules is found. The electron excitation energy migration among the dye molecules in isotropic and oriented polymer matrices as a function of the molecule concentration is investigated. The results obtained can be attributed to partial reduction of the inhomogeneous spectral broadening of electron levels in luminescent molecules under the activator molecule orientation in the polymer matrix.

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Solid state physics

## The external magnetic field effect on the relaxation M$\stackrel{..}{o}$ssbauer spectra of small particles

### V.I. Nikolaev, T.A. Bushina

Moscow University Physics Bulletin 1999. 54. N 4. P. 36

Transformations of the small particle Mossbauer spectra under the paramagnetism-induced superparamagnetism phase transition induced by the applied magnetic field are considered. The magnetic properties of an ensemble of small particles near the Curie point are described using the molecular field theory combined with the Langevin model. Relaxation absorption curves have been numerically simulated with the use of the two-level model. The suggestion is made that the appearance of characteristic relaxation "wings" in the M$\stackrel{..}{o}$ssbauer spectra may be an evidence of the transition of particles into the state of induced superparamagnetism.

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## A berthollide phase in the Pd-Lu system

### A.S. Ilyushin$^1$, N.A. Khatanova$^1$, E.A. Rykova$^1$, Tsetsgeegiin Otgontuul$^2$

Moscow University Physics Bulletin 1999. 54. N 4. P. 43

The X-ray and microhardness data on palladium-lutetium alloys containing $35$; $40,\!06$; $44,\!5$, and $45,\!7$ at.% Lu showed that, after annealing at $1000$$^о$C for $4$ h, the alloys contained not only the Pd$_3$Lu, Pd$_4$Lu$_3$, and PdLu equilibrium intermetallic compounds but also a variable-composition X-phase with a hexagonal lattice and the $c/a$ ratio ranging from 0.45 to 0.52. The X-phase occurs in a wide concentration range in the Pd-Lu system and can therefore be classified with intermetallic compounds of a special type called berthollides according to N.S. Kurnakov.

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Geophysics

## Energy balance in the wind-wave system during the initial stage of wind wave generation

### E.P. Anisimova, K.V. Pokazeev, N.I. Soboleva, A.A. Speranskaya

Moscow University Physics Bulletin 1999. 54. N 4. P. 49

The components making up the wave energy balance equation for the initial stage of wind wave generation have been found. The data measured by these authors and taken from the available literature are used. A refined estimate of the energy coming from the wind fl.ow to the waves by the normal pressure mechanism is proposed.

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## The multipath propagation effect on the accuracy of the media parameter profile reconstruction in the radio occultation experiments

### V.I. Zakharov, V.E. Kunitsyn

Moscow University Physics Bulletin 1999. 54. N 4. P. 53

It is shown that multipath occurrence in complicated cases of satellite-to-satellite signal passage introduces additional distortions into reconstructed media parameter profiles. Separating the rays by their arrival times allows one to reliably discard the beam reflected by the Earth. The multipath propagation effect is local and depends on the experiment geometry. For electron concentration profiles, the range of errors associated with multipath propagation does not exceed 10-12%. It is interesting that the error manifestation regions are restricted in altitude and can be interpreted as wave structures.

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Astronomy

## On the nature of hard X-ray radiation in solar corona during a flare

### S.A. Bogachev, B.V. Somov

Moscow University Physics Bulletin 1999. 54. N 4. P. 60

It is shown that the coronal source of hard X-ray radiation of a solar flare is produced in the collision of the plasma stream from a reconnecting current layer with a magnetic obstacle. The accumulation of reconnected magnetic flux behind the wave front explains the observed source motion velocity.

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Theoretical and mathematical physics

## Coulomb excitation of polyatomic organic molecules in their slow surface sliding

### E.D. Aleksanova$^1$, V.V. Komarov$^1$, A.M. Popova$^1$, H. Jungclas$^2$

Moscow University Physics Bulletin 1999. 54. N 4. P. 64

It is demonstrated that when polyatomic molecules having substructures in the form of unidimensional chains of two-atom dipoles slide over a surface with velocities below the Bohr velocity, collective vibrational excitations {excimoles) develop therein. An analytical expression for the probability of excitation of $k$ excimoles in a chain containing $m$ dipoles, which depends on the sliding velocity and the molecular and the surface parameters, is obtained.

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## The charged $W$-boson propagator in an electromagnetic field in the generalized $R_{\xi}$-gauge

### A.M. Egorov, A.I. Studenikin

Moscow University Physics Bulletin 1999. 54. N 4. P. 68

An exact solution of the equation for the $W$-boson propagator in the generalized $R_\xi$-gauge with consideration for the action of a crossed electromagnetic field has been found. The obtained general expression is consistent with the known result for the propagator in the absence of electromagnetic field, as well as with that in its presence in the cases of the unitary and Feynman gauges. The principle importance of the use of the $W$-boson propagator in the $R_{\xi}$-gauge in studying corresponding loop processes in electromagnetic field is discussed.

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## The problem of measurement interpretation for a fuzzy model of an experiment

### T.V. Matveeva, Yu.P. Pyt'ev

Moscow University Physics Bulletin 1999. 54. N 4. P. 71

The effect of a priori fuzziness of the model experiment on the measurement interpretation fuzziness is demonstrated.

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## Investigation of thermomechanical processes in strongly inhomogeneous media with the use of numerical-analytic procedures

### A.B. Knyazev, G.N. Medvedev, B.I. Morgunov

Moscow University Physics Bulletin 1999. 54. N 4. P. 74

Mathematical models of thermomechanical processes in strongly inhomogeneous media are considered. An iteration procedure for determining the asymptotic expansion coefficients of thermoelasticity equations is described.

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## The sweep method application to calculating the reflection coefficients and determining the field structure in the inhomogeneous absorbing ionosphere

### V.D. Gusev, E.G. Mikhailova, L.I. Prikhod'ko

Moscow University Physics Bulletin 1999. 54. N 4. P. 78

Algorithms for calculating the complex coefficients of reflection and finding the field structure in an inhomogeneous medium with a high-altitude effectivefrequency profile of electron collisions are proposed. The employed sweep method makes it possible to consider the cases of both partial and almost complete reflection of waves from the layer and to find the frequency dependence of the coefficient of reflection.

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Optics and spectroscopy

## The influence of Coulomb attraction in the electron-hole pair on luminescence of phosphor crystals with traps

### A.N. Vasil'ev$^1$, A.V. Nesterov$^2$

Moscow University Physics Bulletin 1999. 54. N 4. P. 82

Within the two-channel model of recombination luminescence, the dependence of recombination parameters on the initial distance between the electron-hole pair components was obtained. Taking into account Coulomb attraction in the electron-hole pair, the quantum yield and the recombination rate were calculated. The suggested model was shown to introduce substantial corrections into the results of calculations based on the model of a "black sphere" with a radius equal to the Onsager radius.

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## Two-wavelength solid-state laser with spatial wave separation

### V.G. Voronin, O.E. Nanii

Moscow University Physics Bulletin 1999. 54. N 4. P. 86

A two-wavelength solid-state YAG:Nd$^{3+}$ laser generating radiation at wavelengths of 1.32 and 1.05 μm has been experimentally implemented and investigated. Weakening the competition between the waves generated in a specially designed dispersive cavity has improved the stability of two-wavelength generation mode.

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Acoustics and molecular physics

## Density pulsations in turbulent flow in front of and behind a shock wave

### O.A. Azarova, E.A. Bratinkova, L.S. Shtemenko, F.V. Shugaev, V.E. Yanitskii

Moscow University Physics Bulletin 1999. 54. N 4. P. 91

The density pulsations in front of and behind a shock wave in a turbulent gas have been studied experimentally and theoretically. The pulsations growth coefficient has been measured and calculated, the change in the pulsations correlation coefficient upon the transition over the shock wave front determined, and the turbulence scale for different shock wave Mach numbers evaluated. The experiments have been carried out in a shock tube, the flow has been turbulized using a net. Turbulence is modeled by a sequence of velocity pulses. The experimental and calculated data are in close agreement.

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Solid state physics

## Formula for series resistance of a solar cell with a conducting antireflection coating

### G.G. Untila, A.S. Osipov, A.B. Chebotareva

Moscow University Physics Bulletin 1999. 54. N 4. P. 94

An analytic expression for the effective series resistance of an $(n^+$-$p)$Si solar cell with an antireflection coating made of an optically transparent conducting oxide such as indium-tin oxide (ITO) is derived. The obtained expression is the resistance dependence on the solar cell parameters, namely, the ITO film and the $n^+$-layer resistances, the contact resistance between the $n^+$-layer and ITO, the width of metallic bands in the current-collecting grid, and on the interband distance.

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