Vol 60, No 5 (2017)

Charge distribution of Kr ions produced under irradiation of neutral atoms by x-ray photons with energy of 1.3 keV is calculated by the Monte Carlo method in the model of the effective atomic potential. The calculated results are in good agreement with recent experimental data and can be used in the development and operation of gas detectors controlling the intensity of free-electron x-ray lasers.

An advanced method of approximating polynomials for simultaneous determination of the temperature and concentration of a hot gas from its spectral characteristics is presented. The technique has been approved with application of the most correct measurements of carbon dioxide transmission function at temperatures 500–1770 K and partial pressures \( {\uprho}_{{\mathrm{CO}}_2} \) = 0.17–1 atm. An arbitrary number (≥2) of spectral centers is used to solve unambiguously the inverse optical problem for the transmission function in the measured spectral region. The influence of the value of the transmission function on its approximation error by the polynomial of a fixed degree is analyzed. Dependences of errors in determining the temperature and concentration of carbon dioxide on the values of its transmission function and the number of the employed spectral centers are obtained. The accuracy of determining experimental values of the thermodynamic parameters with allowance for the error of measuring the transmission function is increased.

For high-precision determination of the rotational-vibrational energies of the ground vibrational state of the SiH₄ molecule, high-resolution rotational-vibrational spectrum of this molecule in the range 600–1200 cm^–1 in which bands of the ν₂/ ν₄ dyad are located is analyzed. As a result, rotational and centrifugal distortion parameters of the ground vibrational state with a root-mean-square deviation of 2·10^–4 cm^–1 are obtained.

A qualitative description of the most accurate experimental differential cross sections of the reaction γp→η′p from the CLAS 2009 Collaboration and unprecedentedly accurate total cross sections of this reaction, measured by the A1 Mainz 2015 Collaboration in the isobaric model of photoproduction has been obtained. Masses and widths of four resonances, extracted from such fits, lay claim to a real existence and lie in the usual mass and width intervals of nucleon resonances. But in order for our model not to contradict the results of measurements of the Σ-asymmetry of this reaction made by the GRAAL 2013 Collaboration, the need arose for an additional resonance with mass equal to the threshold of the reaction under discussion, and width Γ = 110 MeV.

Analytical expressions for complex values of the wave number, refractive index, and the characteristic wave impedance of homogeneous electromagnetic plane waves propagating in a linear, homogeneous, isotropic medium with losses and gain are derived. Formulas for determining the type of normal wave as a function of the values of the real and imaginary parts of the permittivity and permeability are obtained, and conditions for the appearance of positive and negative refraction at the interface of two isotropic media are indicated. In the approach applied here, the concept of a negative refractive index is not used.

The paper presents results of mathematical modelling of plastic deformation in dispersion-hardened materials with FCC crystal system and L1₂ superstructure particles. Research results show that the size and the distance between particles of the strengthening phase affect the strain hardening and the evolution of the dislocation subsystem of the FCC alloy hardened with coherent L1₂ superstructure particles. It is found that increased size of ordered particles or decreased distance between them enhances the abnormal growth in the flow stress and the density of the dislocation subsystem components. Investigations show that prismatic dislocation loops predominate in the dislocation subsystem of materials having a nano-dispersion strengthening phase.

The authors produced an expression for the mechanical equilibrium condition at the phase interface within the force definition of surface tension. This equilibrium condition is the most general one from the mathematical standpoint and takes into account the three-dimensional aspect of surface tension. Furthermore, the formula produced allows describing equilibrium on the fractal surface of the interface. The authors used the fractional integral model of fractal distribution and took the fractional order integrals over Euclidean space instead of integrating over the fractal set.

Using warm, lengthwise grooved-roll processing of the Ti – 0.7 wt.% Si alloy, a nanostructured state is formed in it at 873 K with the grain-subgrain elements measuring about 280 nm. The titanium silicides precipitating during the dynamic strain-induced aging of the alloy are investigated by the methods of high-resolution scanning electron microscopy. It is found that the shape of the silicides is close to spherical, they have an FCClattice and an incoherent interface with the matrix.

Titanium carbosilicide is obtained by the method of self-propagating high-temperature synthesis with titanium and ferrosilicon (with silicon content of 80 mass %) used as initial products. Addition of TiSi₂ to the endproduct with the subsequent heat treatment allows the content of titanium silicide to be increased. The materials based on titanium carbosilicide provide electroconductivity of polymer composite coatings at temperatures exceeding 350°С.

Relationships of volumes during thermal expansion of metals are analyzed. It is demonstrated that metals with BCC structure undergo two-step structural change at the melting point: at the beginning the BCC structure is transformed into FCC structure and then clusters are formed with K = 12 and statistical packing of atoms of the liquid phase. Before melting, hexagonal layer-by-layer (6 + 6) packed Cd and Zn change their structure from K = 6 to K = 8. Metals with FCC structure do not change the number of neighbors before melting, forming clusters with K = 12. It is shown that conditions of pre-melting and polymorphic FCC (HDP) → BCC transformations are reached for the critical volume of thermal expansion caused by leveling of fluctuations of atom and electron densities.

For the BeMN₂ (M = C, Si, Ge, Sn) crystals with the chalcopyrite lattice, model calculations of the electronic structure are performed, equilibrium parameters of the crystal lattice are obtained, band spectra, density of states, and charge distribution densities are calculated within the framework of the density functional theory using a B3LYP approximation. It is found that BeCN₂ is a pseudo-direct-gap crystal strongly compressed along the tetragonal axis (γ = 1.868), whereas BeSiN₂, BeGeN₂, and BeSnN₂ are stretched (γ > 2) direct-gap crystals with band gaps of 7.34, 5.71, 5.07, and 3.24 eV, respectively.

It is shown that the Maxwell–Lorentz equations with a nonlinear source of field type can have solutions which asymptotically are solutions of soliton type, so that the electromagnetic field can be localized in space, and the corresponding electromagnetic soliton can move with nonrelativistic velocity.

Dielectric characteristics of some species of marsh vegetation: lichen Cladonia stellaris (Opiz) Pouzar, moss Sphagnum, and a representative of Bryidae mosses – Dicranum polysetum are studied in the frequency range from 100 MHz to 18 GHz. At a frequency of 1.41 GHz, the influence of temperature in the range from –12 to +20°С on the behavior of dielectric characteristics of mosses, lichens, and peat is studied. The dependences of the dielectric characteristics of vegetation on the volumetric wetness are established.

The diffusion of aluminum ions into zirconium ceramics synthesized from plasma chemical 97ZrO₂–3Y₂O₃ (mol.%) powders is studied by the method of secondary-ion mass spectrometry using a spectrometer PHI 6300. A thin aluminum film deposited on the ceramic surface was preliminary exposed to intermediate annealing at a temperature of 873 K until its full oxidation. Diffusion annealing was performed at temperatures in the range 1520–1820 K. It is established that the typical experimental depth profile of the impurity distribution has two characteristic linear segments with different slope angles. This demonstrates that the diffusion transfer of aluminum ions proceeds simultaneously in the grain volumes and along the grain boundaries. The volume diffusion coefficients are obtained via approximation of the diffusion profiles by solving the Fick equation for diffusion from a thin-film source into a semi-infinite crystal. The obtained values of the diffusion coefficient are in satisfactory agreement with the available literature data.