Vol 58, No 12 (2016)

Photoconductivity in a magnetic field is studied for Faraday geometry on the p-type cadmium – mercury –tellurium films grown by liquid-phase epitaxy on cadmium – zinc – tellurium substrates. From the magnetic-field dependence of the photoconductivity signal under the film illumination from the side of the substrate or from the side of free surface, different values of mobility of minority carriers (electrons) are obtained. It is shown that for the mathematical description of the photoconductivity signal in a magnetic field, two types of electrons – “fast” and “slow” electrons, as well as “heavy” holes can be used.

We present results of computer Monte Carlo simulations of the formation of adsorption layers composed of noninteracting molecules of benzene, anthracene, and pentacene on the Ag(111) surface. The dependences of the chemical potential of the molecules on the density of the molecular layer (surface coverage) are obtained. By means of the thermodynamic integration method the configurational entropy of the molecular layer is evaluated as a function of surface coverage. It is shown that the substitution of benzene by pentacene results in a more than twofold decrease of the maximum entropy of the molecular layer. The presence of steps on the substrate surface also leads to a decrease of the molecular layer entropy. If the distance between the steps is comparable to the linear size of the molecule, the molecules in dense adsorption layers orient preferentially parallel to the step edges.

A scheme of forming an annular high-current relativistic beam (HCRB) from a directly propagating HCRB in a diode with magnetic insulation and toroidal chamber with a constant magnet is described. The code KARAT is used to analyze numerically the HCRB dynamics. It is demonstrated that for a proper relationship of the system parameters the directly propagating HCRB is rolled up into a torus.

This paper presents the theoretical models describing the growth of filamentary channels of nanostructured non-metallic coatings formed by anodizing and microplasma oxidation. The authors identified dependences of the number of pores on the coating thickness. The paper presents graphic dependences of the number of filamentary channels on the process time and the coating thickness. These dependences allow calculating through and surface porosity, and in cases, when the pores are filled with functional material, they allow calculating the concentration distribution of this functional material throughout the coating thickness. The theoretical models enhance our understanding of the nature of anode processes and can be used to describe and forecast the growth and filling of porous coatings, so they can also be used to create functional and bioactive materials.

An MD-simulation of the process of grain-boundary (GB) melting in aluminum is performed. General- and special-type GBs with the [100]-, [110]- and [111]-misorientations are investigated. It is shown that most GBs have lower melting temperatures than that of the single crystal. Grain-boundary melting occurs within the temperature interval from 0.75Тmelt to 0.95Тmelt. Low-angle boundaries and a special Σ11(113) boundary are found to be high-melting.

On the basis of the assumption of the electron density fluctuation at the band degradation, a calculation parameter (the radius R) of the half-width of the probability distribution over the coordinate R is identified at the level of the maximum electron density fluctuation (at a maximum of the Gaussian function). Based on an analysis of the crystallization process and high polymorphic transformations bcc → fcc, the reasons for the formation of bcc, fcc, hexagonal, and tetragonal structures from the liquid phase, as well as for the high temperature bcc → hcp transition in the solid phase are established using the calculated parameter (the radius R) in the solid and liquid phases.

The method of direct simulation of photon trajectories in a stochastic medium is compared with the method of closed equations suggested by G. A. Titov. A comparison is performed for the model of the stochastic medium in the form of a cloudy field of constant thickness comprising rectangular clouds whose boundaries are determined by a stationary Poisson flow of points. It is demonstrated that the difference between the calculated results can reach 20–30%; however, in some cases (for some sets of initial data) the difference is limited by 5% irrespective of the cloud cover index.

Characteristics of cavityless lasing in thin layers of rhodamine 6G (R6G) solutions doped with aluminum, silver, and aluminum oxide agglomerated nanoparticles are experimentally investigated. It is demonstrated that the agglomerates of Ag, Al, and Al₂O₃ nanoparticles in R6G solutions lead to a significant (by more than two orders of magnitude) decrease of the cavityless lasing threshold in a wide range of concentrations of the agglomerates compared to the luminescence threshold in R6G solution without nanoparticles.

Results of spectral-luminescent and electroluminescent investigations of organic semiconductor polyfluorenebased copolymers in diode devices emitting dark blue, green, red, and white light are presented.

Round-the-clock measurements of the black carbon size distribution in the submicron near-ground aerosol of Western Siberia performed in 2014 by the diffusion method developed by the authors are analyzed. It is revealed that the tendency for decreasing the volume median diameter and the amplitude of distribution of the black carbon is traced in the seasonal dynamics of the average monthly black carbon particle size distribution (approximated by a single-mode lognormal function) during winter-to-summer season transition. The shape of the black carbon size distributions is in agreement with measurements by other well-known methods in different geographic regions.

The dispersion law and the anomalous magnetic moment of a neutrino in a magnetized electron-positron plasma are investigated as functions of the magnetic field strength, the polarization state, energy, direction of motion, and mass of the neutrino, and the parameters of the plasma. The calculation was performed by the method of the time Green’s functions at finite temperature. Results for a massive neutrino in the limiting case are compared with the results of other authors, obtained earlier for a massless left-handed neutrino.

One case of the dynamics of a scalar order parameter on a torus in the presence of pumping and nonlinear decay is considered. The existence of dissipative solitons is revealed.

In this work, the behavior of the Stark component intensities of spectral lines in the emission spectrum of the helium atom excited by an alternating circularly polarized electric field is studied theoretically. The line intensities of an atom in the electric field are calculated within the framework of the method of energy matrix diagonalization. Based on the calculated results, a number of regularities have been revealed in the behavior of the Stark component intensities of the helium spectral lines with changes of the electric field strength.

A new integrable modification of the LJ-potential and a continual approach are used to investigate the interaction between a thin film (graphene) and gas molecules. It is shown that this technique allows determining the characteristics of a van der Waals-type interaction between molecules and graphene films of a variety of shapes. It is found that an unperforated graphene (planar or buckled) is impermeable for molecules with the energies consistent to the room temperature of a gaseous medium; hence, it has to be perforated in order to be used as a separator. Penetration of the molecules through the openings in a buckled graphene is somewhat different from that through a planar graphene, though these differences are insignificant. It is demonstrated that the data obtained on the planar graphene (most useful for theoretical research) are also valid for the really existing buckled (ruled-surface or chessboard) graphenes. When a graphene is used as a separator, its shape does not play the leading role in determining its principal property – permeability.

Point dipoles are scattering elements of a medium. The medium consists of plane-parallel dipole monolayers influencing one another. Dipole fields are completely taken into account. The fields inside the medium and the reflected fields are calculated. The extinction theorem is analyzed in detail. The mechanism of rotation of the magnetic field vector during refraction is elucidated. A reason for the absence of the fourth wave propagating from the medium toward the boundary in the conventionally employed boundary conditions is elucidated. It is demonstrated that the interdipole interaction within a single monolayer leads to the occurrence of spatial harmonics in forward propagating radiation.

The Wong equations, which describe the motion of a classical charged particle with isospin in an external gauge field, are considered. The structure of the Lie algebra of the linear integrals of motion of these equations is investigated. An algebraic condition for integrability of the Wong equations is formulated. Some examples are considered.

A solution is obtained for the Ising model on the Bethe lattice comprising a mixture of magnetic and nonmagnetic atoms in a thermodynamic equilibrium. The concentration and temperature dependences of spontaneous magnetization, the Curie temperature, and the percolation threshold are found together with the pair correlation functions of three types that characterize the arrangement of impurity atoms and the correlation of magnetic moments. It is demonstrated that the system with mobile impurities in the thermodynamic equilibrium can be brought closer to the system with frozen impurities by adjusting the parameters of interatomic interaction.

A flow of physical events (photons, electrons, etc.) is studied. One of the mathematical models of such flows is the modulated MAP flow of events circulating under conditions of unextendable dead time period. The explicit form of the probability density of interarrival interval of the flow is presented together with the explicit form of the joint probability density of two adjacent intervals in the observed flow. The conditions for recurrence of the observable flow of events are presented.