Том 11, № 5 (2017)

The contribution to the RYDMR spectrum from an elementary event of collision of two triplet excitons during their mutual annihilation is calculated, and the reverse process of photogeneration of a pair of triplet excitons in a molecular crystal are considered. The interaction between the excitons in the cell is assumed weak in comparison with the Zeeman splitting and the fine-structure parameters for the triplet state of each of the molecules. For both the annihilation of excitons and the photogeneration of a pair, the RYDMR signal from a single-crystal sample disappears at certain orientations of the crystal relative to the external magnetic field. This effect was previously experimentally observed for the anthracene−tetracyanobenzene crystal and was explained in the case of stationary optical excitation of the molecule. The results obtained in this paper make it possible to consider an arbitrary, not only stationary, mode of irradiation sample. An interval of angles between the static magnetic field and the crystallographic axes of the crystal within which the lines in the spectrum can disappear is determined. The possibility of using the RYDMR method for studying nanosized objects, for which additional peaks in the RYDMR spectrum may arise, is briefly discussed.

The pK_a values of some phthalhydrazide derivatives were calculated using ab initio and two density functional methods to obtain information about their reaction conditions. The results showed that pK_a1 was influenced by structural modification as it varied between 0.47 and 6.99, and that pK_a2 was relatively less variable from 16.66 to 21.53. The high values of pK_a2 revealed that a strong alkaline solution was necessary for all chemiluminescent reactions of discussed phthalhydrazide derivatives.

The physical principles and most effective modern technologies for detecting and identifying explosive agents and devices and the analytical potential of these technologies were considered to solve the problems of antiterrorist security and countermeasures against terrorist attacks using explosive devices based on explosive agents. Particular attention was paid to the possibility of detecting explosive agents and devices, in particular, during automated control at the entrance to airports, railway stations, and various institutions and organizations and security check of suspicious persons, luggage inspection, etc. An analysis of the possibilities for identifying explosive agents and devices can evidently create conditions for expanding the existing technologies or combining them with new technologies for detecting not only various types of explosives, but also narcotic drugs, firearms, cold weapons, radioactive substances, poisonous substances, highly toxic substances, biological agents, etc.

The conversion of phenylone polymer (poly-m-phenylene isophthalamide) at 293 K under the action of a nitrogen dioxide−oxygen gaseous mixture and nitrogen dioxide and oxygen individually is studied by the ESR method. In the first case, aryliminooxyl and arylacylaminoxyl free radicals are recorded, whereas in the second, diarylaminoxyl and phenoxy free radicals. The presence of phenolic and phenyl benzoate polymeric products in nitrated phenylone is detected by IR spectroscopy. The mechanisms of reactions occurring in both the oxidation modes are considered.

The characteristics of the combustion of Ti + 0.5C, Ti + 0.75C, and Ti + C powder and granular mixtures in a flow of inert (argon) and reactive (nitrogen) gases at various pressure differences are studied. It is shown that the influence of the pressure difference on the burning velocity of the powder mixture decreases with increasing fraction of carbon in it, but a pressure difference of 1 atm producing practically no effect on the burning rate of the Ti + C mixture. The data obtained are indicative of a nonequilibrium mechanism of the combustion of Ti + xC granular mixtures in a nitrogen coflow, in which case the sequence of chemical reactions in the combustion wave is determined by the kinetic characteristics of the interaction of titanium with nitrogen and carbon. It is concluded that the reactive gas flow ignites the surface of the granules and thereby leads the propagation of the combustion wave. It is established that, for all the mixtures studied, the mechanism of the combustion of a granular charge in a nitrogen flow is fundamentally different from the combustion of a powder charge under the same condition.

The production of hafnium aluminides from mixtures of hafnium or its oxide with aluminum in the combustion mode is impossible because of a near-zero thermal effect. The present study is aimed at stimulating autowave chemical transformation with the help of energetic formulations and producing cast hafnium aluminides by means of combustion methods. The characteristics of the autowave synthesis and the conditions for producing cast hafnium aluminides are determined, and their composition and structure are investigated.

A material based on polylactide and iron(III)–tetraphenylporphyrin complex is prepared. The UV electronic spectra of the samples indicate the presence of porphyrin microinclusions in the polylactide matrix. According to optical microscopy, these inclusions have a size of 50–200 μm. It is determined that the melting point of the polylactide matrix decreases by 1–3°C with increasing porphyrin content in the composition. An experiment at a temperature of 40 ± 1°C shows that the degree of crystallinity of the polylactide matrix of the compositions varies insignificantly and does not exceed the degree of crystallinity of the original pure polylactide. In this case, the melting point remains almost unchanged.

The possibility of forming supramolecular structures of a polymer complex consisting of products of polycondensation of boric acid and imidazole from aqueous solutions and melts of the components is shown. Depending on the ratio of the components, the heat resistance of the polymer complex lies within 60 and 480°C. The effect of sharp decrease in the heat resistance of the complex and the degree of polycondensation of boric acid upon a slight increase in the imidazole concentration above the stoichiometric ratio is revealed, which was explained by the “blocking” of hydroxyl groups by imidazole molecules and, correspondingly, by a significant decrease in their chemical activity. The energies of the intermolecular bonds in the complexes are calculated.

The effect of additives of cobalt and zirconium oxides on the conductivity of nanostructured composites based on indium oxide is studied. It is shown that addition of up to 20 wt % ZrO₂ to In₂O₃ leads to a sharp decrease in the conductivity of the composite. For the Co₃O₄−In₂O₃ system, the conductivity decreases up to a Co₃O₄ content of 60 wt %, after which it increases. At a Co₃O₄ content in the Co₃O₄−In₂O₃ system of up to 60 wt %, n-type conduction takes place, changing to p-type at 80 to 100 wt % Co₃O₄. Zirconium oxide exhibits practically no n-type conduction, so electric current in the ZrO₂−In₂O₃ system flows through In₂O₃ nanocrystals, i.e., n-type conduction takes place. Possible causes of the observed effects are considered.

We consider different approaches to calculating the ion composition in the lower ionosphere and use two methods for modeling the concentration of molecular ions. The first method allows us to solve an equation with an effective recombination coefficient for the total concentration of molecular ions, and the second method calculates their concentrations separately. Numerical experiments were performed using a global self-consistent model of the thermosphere, ionosphere, and protonosphere (GSM TIP) for the conditions of March 16–20, 2015. We show that the second method, which provides a more accurate approximation, leads to significant consequences. Due to a strong change in the calculated concentration of ions in the E-region, the conductivity varies thus affecting the qualitative and quantitative behavior of the electric dynamo field at low and equatorial latitudes. Even without mesospheric tides and the electric dynamo field in the F-region, the calculation of partial concentrations of molecular ions makes it possible to qualitatively reproduce the outburst of the eastern electric field observed at the geomagnetic equator and in its low-latitude vicinity. During geomagnetic disturbances, a more accurate approximation leads to significant changes in the pattern of electron density perturbations at the heights of the ionospheric F-region in comparison with that obtained with the calculated total concentration of molecular ions.