Influence of density fluctuations on the equation of state

The influence of inhomogeneity of particle density on the equation of state has been considered in the approximation of homogeneous fluctuations. The formula for the relative mean square fluctuation has been derived taking into account intermolecular interaction. It has been shown that the density fluctuations cannot be neglected near the coexistence curve. This curve has been obtained without recourse to the Maxwell construction; unphysical parts of the van der Waals isotherms in fact never appear in the theory. Experimental parameters have not been used.     

An investigation of the reliability of the Galerkin-Petrov method

The Galerkin-Petrov method is applied to the determination of the ground state energy of the beryllium atom. The basis set of the coordinate subspace consists of correlated wavefunctions of the combined configuration-interaction-Hylleraas type. The basis set of the projective subspace is of the configuration-interaction type. The usefulness of a previously proposed way of characterization of pairs of subspaces has been further confirmed. Experience in constructing close pairs of subspaces gathered in the case of two-electron systems is used for the larger system. Two methods for constructing pairs of subspaces are used in the calculations.     

Vibrations of parametrically excited systems

The paper is concerned with a set of linear differential equations with time-dependent parameters given by trigonometrical series. Derived formulas make it possible to examine stability, to find boundaries of the regions of instability and to estimate the steady state response amplitude of forced vibrations.     

Thermal decomposition of complexes of antimony(III) bromide with hydrobromides of some aromatic amines

Thermal studies have been carried out on crystalline complexes formed between antimony(III) bromide and hydrobromides of some aromatic amines in concentrated hydrobromic acid solutions. Thermal analysis curves of the compounds under study are presented. Kinetic parameters of the thermal decomposition reactions were calculated from the TG curves using the Horowitz—Metzger method. A comparison of the thermal stabilities of the complexes was made.     

The nature of excitonic complexes in ZnTe

Uniaxial stress experiments were used to investigate the nature of the luminescence lines observed at low temperatures in ZnTe in the vicinity of the absorption edge. The single crystals used in this experiment were grown from solution of ZnTe in tellurium. Both “as-grown” crystals and crystals annealed in Zn vapour were investigated. The most intense line in “as-grown” crystals is attributed to an exciton bound to a neutral acceptor. The binding energy of the exciton in this center is 6 meV. After annealing a new center appears in the same spectral region. Stress experiments as well as the temperature dependence of the intensity of the luminescence indicate that this center is a complex consisting of an exciton and an ionized donor. Splitting of J = 1 (Γ₅) and J = 2 (Γ₃ + Γ₄) levels was found to be 1.2 meV.     

Influence of nonlinear effects on the statistical properties of a high power density laser beam

The second-order intensity correlation function g⁽²⁾(0) of a laser beam passing through a nonlinear medium has been experimentally found to be a decreasing function of the power density in the medium.     

Interference maxima in the backward excitation curve of α-particle elastic scattering on medium-weight nuclei

Excitation functions for the elastic scattering of α-particles from Ni, Co and Cu at θ_lab = 179° were measured in the lab energy range 22.75–28.40 MeV, as well as some angular distributions for Co(α, α). Broad maxima with a width of about 2.5 MeV were found in the excitation functions. It is shown that a simple four-parameter optical model of the interaction is able to reproduce the angular distributions as well as the excitation functions. Examination of the Argand diagrams leads to the conclusion that the maxima in the excitation curves are formed as a result of a coherent superposition of a number of partial waves, none of which behaves in itself in a resonance-like manner.     

Laser properties of praseodymium pentaphosphate single crystals

PrP₅O₁₄, Pr_xLa_1−xP₅O₁₄, and Pr_xY_1−xP₅O₁₄ (0≦x≦1) single crystals of laser quality were synthesized and their crystallographic and optical parameters measured. Laser emissions in the visible (λ=637.4 nm) with no mirrors in place (superradiance) and also in various optical resonators have been observed.     

A new isotherm equation for multilayer adsorption on heterogeneous surfaces yielding the Dubinin-Radushkevich isotherm in the submonolayer region

The Cerofolini procedure for obtaining multilayer adsorption isotherms on heterogeneous surfaces is generalized, to take into account the full form of the BET equation as the local adsorption isotherm.