R e g u l a r p a p e r s

Theoretical and mathematical physics

Moscow University Physics Bulletin 2002. **57**. N 5. P. 1

The generation of a magnetic field in a swirling semi-bounded jet (screw dynamo) is considered. Conditions for an exponential growth of the field in the coordinate and for an exponential growth of the field in time at a fixed point have been obtained.

Show AbstractMoscow University Physics Bulletin 2002. **57**. N 5. P. 6

A transcendental equation for the complex energy has been obtained on a basis of an exactly solvable $3D$ model for a short-range potential and the Green's function in an intense electromagnetic field combining a constant magnetic field and the field of a circulary polarized wave. Parameters of the quasistationary states of an electron in the $\delta$-potential with consideration for an intense external field of complicated configuration have been calculated. Possible stabilization of the decay of a spinor and a scalar particles in the bound state by means of an intense magnetic field has been cleared up. It is argued that with consideration for the results obtained, the commonly accepted idea of the stabilizing role of a strong magnetic field in the atom ionization should be revised.

Show AbstractMoscow University Physics Bulletin 2002. **57**. N 5. P. 15

Quantum systems containing substructures of ordered identical components that can be represented by quantum oscillators with two energy levels are considered. It has been demonstrated that the collective vibrational excitation of these substructure components leads to a superfast transport of the vibrational energy inside the quantum system and to its fragmentation. An analytical expression has been obtained for the fragmentation rate of quantum systems with many degrees of freedom in IR fields. The fragmentation process of such systems in external IR fields has been shown to depend in a resonance fashion on the field intensity and on the number of identical degrees of freedom, i.e., the number of identical substructure components.

Show AbstractMoscow University Physics Bulletin 2002. **57**. N 5. P. 21

The method of integral transformations related to studying the Laplace images of wave functions is applied to determine the discrete spectrum of radial Schr$\stackrel{..}{o}$dinger's equation with arbitrary attraction potential. The summation of series has been performed in matrix elements of the characteristic equation, which are represented in the form of formal expansions in inverse powers of energy. The possibilities of the method have been demonstrated with the examples of the generalized Yukawa potential and the screened Coulomb potential; the method can also be successfully applied to other potentials.

Show AbstractMoscow University Physics Bulletin 2002. **57**. N 5. P. 27

A long-term prediction of mean monthly temperatures by the possibility theoretical method of measurement reduction in the presence of a priori information about input data is studied. The possibility of the event is oriented to a relative estimation of the truth of the event on a rank scale, where only the relations "larger", "smaller", or "equal" have a meaningful interpretation. Thus, the prediction to have a certain temperature in a given month is characterized as "more" or "less" possible.

Show AbstractMoscow University Physics Bulletin 2002. **57**. N 5. P. 32

Binary molecular diffusion and pressure driven fluxes of gas in porous media have been studied. A 2-dimensional model of gas transport in porous media in the field of nonzero gradients of pressure and concentration has been developed. Spatial distributions of oxygen concentration and fluxes in a porous diffuser of a polymer electrolyte hydrogen fuel cell have been analyzed as a function of geometric and physical parameters of the electrode. 3-dimensional generalization of the model has been performed. Possible application to oxygen flow modeling in electrodes of polymer electrolyte fuel cells has been discussed for two simple configurations of gas supply channels, i.e., serpentine and interdigitated.

Show AbstractAtomic and nuclear physics

Moscow University Physics Bulletin 2002. **57**. N 5. P. 41

Method has been presented for simultaneous and separate determination of spectral and dose characteristics of $\alpha$-, $\beta$-, and $\gamma$-radiation, low-energy particle parameters, as well as for determination of the radionuclide type in the substance under study. The method is based on measuring the specific energy loss $\Delta E$ of a particle simultaneously with measuring energy $E$ by semiconductor detectors, and also by prograI11mable memory devices for storage of preliminarily calculated dependencies $\Delta E(E)$ for each type of particles and further comparison with measurements.

Show AbstractAcoustics and molecular physics

Moscow University Physics Bulletin 2002. **57**. N 5. P. 48

Dynamics of a proton has been considered in a non.stationary potential under the effect of a quasiharmonic signal, a colored noise simulating thermal fluctuations of atoms and atomic groups, and an impulse parametric excitation simulating the influence of the carbon atom in the peptide bond on the potential, wherein the proton transfer takes place. The behavior of the system has been studied with various colored noise and pulse action par8.Illeters. The wave function has been computed on the basis of the spectral method of splitting the evolution operator implemented on the cluster in the Research Computer Center of Moscow University.

Show AbstractSolid state physics

Moscow University Physics Bulletin 2002. **57**. N 5. P. 54

A general equation for a thermoelectronic emission current has been obtained with regard to quantum image forces described in terms of the theory of the electron polaron at the contact between two media developed by the authors. It was demonstrated that noticeable deviations of field dependence of the tunnel current from the known classical results should occur in the field region $F>10^6$ V/cm.

Show AbstractMoscow University Physics Bulletin 2002. **57**. N 5. P. 60

The feasibility of obtaining a submicron resolution in the X-ray microscope using as an optical element a crystal-monochromator in an extremely asymmetric scheme of diffraction has been demonstrated. The dependence of resolution on unit parameters has been studied. The optimal geometry of the experiment and the wavelengths for obtaining a submicron resolution has been determined.

Show AbstractMoscow University Physics Bulletin 2002. **57**. N 5. P. 66

X-ray diffraction measurements have shown that along with the equilibrium intermetallic compound Pd$_4$Tb$_3$, a berthollide phase is formed in the Pd-44.6 ат.% Tb cast alloy. The parameters of the hexagonal lattice of the berthollide are a = 13.405 A, and c = 6.154 A. Subsequent to annealing at 500$^о$C for 100 hours berthollides experience a phase transition and change into equilibrium intermetallic compounds Pd$_4$Tb$_3$ + PdTb.

Show AbstractMoscow University Physics Bulletin 2002. **57**. N 5. P. 73

We have studied the effect of temperature on the relationship between the domain wall (DW) velocity $V$ and the active magnetic field strength $H$ in (Bi,Eu)$_3$(Fe,Ga)$_5$O$_{12}$ single-crystal garnet-ferrite films grown by the liquid-phase epitaxy technique from a supercooled solution-melt on (Gd,Ca)$_3$(Mg,Zr,Ga)$_5$O$_{12}$ substrates of different orientation. These films are shown to have a DW velocity of $V>1$ km/s near the moment of momentum compensation point, this rate changing by 34% at $H=200$ Oe in the temperature range $T=25$-$100$$^о$C under study in the case of (110) orientation where orthorhombic magnetic anisotropy is induced.

Show AbstractGeophysics

Moscow University Physics Bulletin 2002. **57**. N 5. P. 78

This paper is devoted to the determination of the role of the gravitational-capillary mechanism in the formation of the thermal structure of the near-the-surface layer of the ocean, specifically in the presence of surfactants. The results of numerical experiments on transfer processes carried out with the mathematical near-the-surface layer model developed at the State Institute of Oceanography have been described.

Show AbstractMoscow University Physics Bulletin 2002. **57**. N 5. P. 84

We have measured the thermal- and slow-neutron fluxes of two systems: on the soil and over a water area (Lake Seliger) and on the soil and on a glacier (the Pamirs). The information obtained confirms that the contribution from the Earth's crust to the total flux of thermal and slow neutrons in the lower atmosphere is comparable with the contribution from cosmic rays. The main contribution from the Earth's crust as a source of neutrons of such energy is associated with natural radioactivity.

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

Atomic and nuclear physics

Moscow University Physics Bulletin 2002. **57**. N 5. P. 90

The capabilities of a new 70-Mev electron accelerator as a source of hard $\gamma$-radiation have been analyzed.. A computer simulation technique is used to determine optimal conditions for the generation of bremsstrahlung radiation within various energy ranges and directionality of photons. The characteristics of photon beams designed for irradiating objects of different geometry have been indicated.

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