Vol 10, No 2 (2016)

Characteristic features of net chemically induced dynamic electron spin polarization (CIDEP) P_n in triplet–radical (TR) quenching are analyzed in detail within the framework of a general model that enables one to analyze CIDEP both numerically and analytically. This model also makes it possible to accurately describe the nonadiabatic transitions between the terms of the TR-pair spin Hamiltonian that lead to CIDEP generation. The proposed theory yields a simple analytical dependence of P_n on the parameters of the model. In particular, it is shown that, within a wide region of parameters, the dependence of P_n on the coefficient of relative TR diffusion D_r is described by a simple linear relation: \(P_n^{ - 1}\left( {{D_r}} \right) = {Q_0} + \overline {{q_n}} {D_r}\) (with Q₀ and \({{q_n}}\) independent of D_r). It is also demonstrated that the numerical and analytical results obtained are very useful in analysis of experimental data, as demonstrated by analyzing the experimental dependence of P_n on D_r.

The dissociative excitation of the singly charged manganese ion in collisions of electrons with MnI₂ molecules is experimentally studied. At exciting electron energy of 100 eV, 16 dissociative excitation cross sections were measured. The studied transitions occur within the quintet and septet term systems in the absence of intercombination transitions. The measured values of the cross sections are compared to similar values obtained previously in studies of e–MnCl₂ and e–MnBr₂ collisions.

The properties of bismuth-containing luminescent materials prepared by impregnating a porous glass with an aqueous solution of bismuth and aluminum salts followed by thermal treatment are studied. The formation of a variety of bismuth-containing centers luminescent in the near infrared range of the spectrum is revealed, one of which is the Bi⁺ monocation. At high temperatures, along with it, bismuth-containing cluster-type luminescent centers are apparently formed.

The photoionization of the C₆₀ and C₂₄₀ fullerenes by ultrashort electromagnetic pulses of subfemtosecond duration is studied. The probability for the process to occur during the action of the pulse as a function of the pulse duration is calculated for different carrier frequencies. The spectrum of photoelectrons emitted during the ionization of the fullerenes by a pulse with a corrected Gaussian shape is calculated.

Kinetic theory is used to treat the characteristics of the decomposition of the disilane molecule into two non-identical radicals in a wide range of growth temperatures and at low gas pressure in the reactor. The conditions for determining surface concentration are established and the possibility of the existence of an unambiguous relationship between the rates of decomposition \({v_{SI{H_3}}}\) and \({v_{SI{H_4}}}\) various fragments of the molecule is demonstrated. A strong dependence of the rate of decomposition of the molecules of the working gas on its pressure was revealed, which suggests that the film growth rate is mainly dependent on the rate and mode of the pyrolysis process on the surface of the growing layer. It is shown that a model of disilane decomposition into two non-identical fragments with the concurrent transfer of all the hydrogen atoms of the molecule onto the silicon growth surface is most preferrable for an adequate description of the pyrolysis process at temperatures within 400–800°C. Non-physical features of the temperature dependences of the kinetic coefficients appearing in the model of decomposition of disilane into two identical radicals is completely eliminated if the hydrogen atoms are transferred onto the growth surface at the chemisorption stage.

The introduction of molybdenum nanoparticles in MoSe_x thin films formed by pulsed laser deposition led to changes in the film structure. The base planes of the layered atomic packing of the MoSe_х matrix around Mo nanoparticles rotated; as a consequence, the edge sites that formed during the “breaking” of the Se–Mo–Se layered atomic packing came out to the film surface. At high nanoparticle concentrations, this effect led to high density of edge sites possessing increased catalytic activity (compared with that of the base planes) for initiating the electrochemical evolution of hydrogen in a 0.5 M H₂SO₄ solution. Voltammetric measurements at room temperature showed that when the carbon cathode was coated with MoSe_x thin films under optimum conditions, the hydrogen overvoltage considerably decreased, and the cathodic current increased. The results indicate that developments in the field of preparation of nanostructured electrodes based on layered transition metal dichalcogenides show promise as an alternative to expensive electrodes based on platinum group metals for electrocatalysts of hydrogen evolution.

The kinetic results of the radical chain oxidation of methyl linoleate (LH) in micelles were given. The oxidation rate depends on the average number of substrate molecules in the micelle and is almost independent of the micelle concentration under the given conditions. The chain propagation and termination were assumed to predominantly occur inside the micelle. Possible reasons for linear chain termination during the oxidation of polyunsaturated fatty esters in microheterogeneous systems were discussed.

The results of a comparative study of the characteristics of surface combustion in the infrared mode on a flat and volumetric foamed-metal matrix with a ceramic (alumina) coating are reported. The coating of thickness ~200 μm was applied by using the detonation method. It was shown that the covering of the matrix with a material having a lower emissivity and thermal diffusivity causes the flame front to immerse into the matrix and increases the surface layer temperature. For combustion on a flat matrix at a firing rate of ~75 W/cm², the concentrations of nitrogen oxides and carbon monoxide were up to two times lower. For combustion in a volumetric matrix at a firing rate of ~30 W/cm², the reduction in the concentration of nitrogen oxides was two to three times lower.

Specific features of the combustion of a titanium–carbon black granular mixture in a quartz tube blown with nitrogen is studied. In contrast to the previous studies, titanium with increased hydrogen content is used. The gas flow (cocurrent filtration) is produced by applying a fixed pressure differential less than 1 atm across the inlet and outlet of the tube. The characteristics of the combustion of a Ti + 0.5C granular mixture in a nitrogen flow are investigated. It is shown that an increased content of hydrogen in titanium leads to the formation of a two-front combustion wave. It is demonstrated that the first and second fronts of the two-front structure arise due to the interaction of the charge with nitrogen. The velocities of propagation of the fronts increase with the nitrogen pressure differential.

The wide scatter of the values of the measured detonation cell size in fuel + air mixtures restricts the applicability of this parameter in the estimation of the geometric limits of detonation propagation, including in rectangular channels whose height is much larger than their width. The critical channel height for the propagation of detonation has been experimentally determined for hydrogen + air, propane + air, and ethylene + air mixtures. In order to reveal the specific features of the propagation and decay of detonation in a narrow channel, numerical simulation has been carried out for a hydrogen + air mixture with account taken of the cellular structure of the detonation wave.

Models of poly-p-xylylene and its chlorine substituent polymers were established and structural optimized with Molecular Dynamics (MD) in Material Studio (MS) software. The densities and glass transition temperatures (T_g) calculated from the optimized models were consistent very well with the experimental data. The free volumes and their distributions in these polymeric models were obtained using the Atom Volumes and Surfaces tool. The results showed that the amount of free volume for each model was very small, especially for those free volume cavities of diameter larger than 2.8 Å, which made it difficult for the molecules of diameter larger than 2.8 Å penetrating in the polymer. The diffusion, solubility and permeability coefficients of some gaseous molecules in these models were also calculated based on the combined methods of MD and Great Canonical Monte Carlo (GCMC), which presented the same or 1–2 higher order of magnitude with experimental values. The trajectories of penetrant molecules diffusing in polymeric models demonstrated that the molecules transferred or moved in amorphous regions between spherical crystals with a “hopping diffusion” behavior.

A simple design of a magnetic separator based on a membrane made of a laser-perforated ferromagnetic foil has been proposed. The separator is primarily intended for analytical and research purposes. The developed magnetic separator of the proposed design has been tested in the separation of a composite aqueous suspension of magnetite nanoparticles adsorbed on hydroxyapatite microparticles. Separation efficiency has been determined via measuring the magnetic moment by the ferromagnetic resonance method; the suspension particle size has been found by dynamic light scattering before and after the separation process. It has been shown that all the particles with a diameter of more than 500 nm are retained during separation; the magnetization of the fraction decreases twofold after passing through the membrane.

Based on the self-consistent cluster approximation of an effective medium for random walk on a lattice of randomly located traps, the issue of the self-averaging of the diffusion coefficient in the subdispersive mode is examined. It is demonstrated that, in this mode, the diffusion coefficient self-averages slowly according to a power law in the case of three-dimensional space, whereas for the one- and two-dimensional cases, it self-averages poorly, with its relative fluctuations decreasing abnormally slowly, according to a logarithmic law.

A one-dimensional model of the rise of O^– negative ions generated by a ground-based external source to altitudes of several kilometers under the action of the Earth electric field is developed. The model takes into account the contributions from the diffusion and drift of the ions, as well as the effect of a rising air flow. The characteristic time of rise of negative ions to an altitude of 2 km is determined, altitude distributions of the concentration of ions are obtained, and the distortion of the Earth electric field due to the presence of an excess of negative ions is demonstrated.

Electrodynamic and plasma chemical tropospheric processes have been considered in order to develop a cloud control technology. A mathematical model has been constructed for ionic flow from a ground-based plasma generator in the electric field of a charged cloud. The problem of the rise of four types of anions and four types of cations and the problem of electric field strength have been solved using a system of transfer equations and the Planck equation. The final distribution of the charged particle concentrations has been analyzed, and it has been demonstrated that a considerable quantity of O₃^- can rise up to an altitude of 2000 m.