Vol 11, No 6 (2017)

Inelastic collisions of slow electrons with cobalt dichloride molecules, leading to the formation of excited cobalt atoms in odd sextet states, are experimentally studied. At an incident electron energy of 100 eV, thirty six dissociative excitation cross sections are measured for levels belonging to the z⁶D°, z⁶F°, and z⁶G° terms. In the electron energy range of 0–100 eV, ten optical excitation functions are recorded. The full cross sections for the dissociative excitation of the cobalt atom levels and the contribution of cascade transitions to their population are determined. The cross sections for electron–molecule and electron–atom collisions are compared.

The kinetics of fast fluorescence decay in organic semiconductors due to the splitting of the excited singlet state S₁ into a pair of triplet (T) excitons is significantly influenced by the process of reverse TT annihilation. It is shown that a correct interpretation of this effect requires taking into account the stochastic migration of T excitons. A two-state model (TSM) is proposed for describing the effect of migration on the kinetics of TT annihilation and, thus, on the kinetics of the fission of the S₁ state. In the TSM, the migration effect is interpreted in terms of transitions between the [TT] state of the interacting excitons (at small T−T distances) and the [T + T] state of freely diffusing excitons (at large T−T distances). Within the framework of the TSM, an analytical expression for the fluorescence decay kinetics (FDK) \(I_{S_1 } (t)\) from the S₁ state is derived. This expression is used to describe the FDK measured in amorphous rubrene films in the absence of the magnetic field (B = 0) and in the magnetic field B = 8.1 kG. Adjusting the parameters of the model makes it possible to reproduce the experimentally measured FDK with good accuracy. An analysis of the theoretical FDK obtained revealed a significant contribution of T migration to \(I_{S_1 } (t)\), which manifests itself, in particular, in the characteristic dependence \(I_{S_1 } (t) \sim t^{ - 3/2}\) at long times.

A method was developed for calculating the vibronic potential energy surfaces (PESs) of atmospheric complexes consisting of orbitally degenerate Rydberg nitrogen and oxygen molecules and the molecules of a neutral medium in the ground electronic state. The degenerate states are formed as a result of l-mixing in the D and E layers of the atmosphere during the periods of increased solar activity. The complexes are populated in the nonequilibrium two-temperature plasma and are responsible for the incoherent additional background radiation in the decimeter (microwave) and terahertz (IR) bands at an altitude of 80–110 km from the Earth’s surface. To describe the interaction of a weakly bound electron with a singly charged molecular ion and a neutral molecule of a gas medium, the formalism of the multichannel quantum defect (MCD) theory was used. Quantum-chemical calculations of the dependences of the scattering lengths, polarizabilities, and quadrupole moments of the main atmospheric molecules N₂ and O₂ on the interatomic distance were performed. The specific features of the behavior of vibronic PESs of Rydberg complexes for large values of the principal quantum number (n ≫ 1) were analyzed. The vibronic PESs of orbitally degenerate states were constructed. They are necessary for determining the positions and shape of the vibronic minima of the l-mixing cross sections of the N₂ and O₂ Rydberg molecules in the D and E layers of the Earth’s atmosphere, where the delay times of satellite positioning signals should be minimum. The possibility of “quantum chaos” appearing in the Rydberg complexes at sufficiently large n values and angular momenta of the weakly bound electron was noted.

It was demonstrated that the luminous cloud arising during an explosion in air initiated by an electric discharge produces superluminescence and laser generation in the visible spectrum. Both these types of radiation presumably originate from the stimulated emission of NO* (blue light) and NO*₂ (orange and red) molecules and N₂O(¹S) exciplexes (green). In addition, if the process occurs inside an optical resonator, the mixture of nitrogen oxidation products with air autoignites.

The characteristics of surface-combustion IR burners with permeable wire material matrices operating on natural gas−air mixtures are studied. The experiments are carried out with matrices of two designs: a flat two-layer matrix and a volumetric cylindrical matrix. The composition of the combustion products is determined, and the temperatures of the working surface and the back surface of the matrices are measured at burning power densities from 10 to 90 W/cm². It is shown that burners with a volumetric matrix are characterized by a higher efficiency of conversion of combustion energy into thermal radiation and lower emissions of carbon monoxide and nitrogen oxides as compared to burners with a flat permeable matrix.

Experiments carried out in a rapid-injection setup with tangential introduction of the mixture into the reactor show that the mixtures self-ignite at temperatures substantially lower than the values reported in the literature. The measured ignition delay times do not exceed 0.1–0.2 s, although thermal conditions in the reactor allow the mixture to ignite with delays of more than 10 s. Videorecording shows that the mixture spontaneously ignites in a small volume at the center of the reactor; i.e., tangential mixture injection produces a vortex with a hotspot having a temperature at its center by more than 200 K higher than that of the reactor walls. An obstacle destroying the vortex eliminates the anomalous behavior of the self-ignition process. Temperatures measured at the center of the reactor with a thermocouple confirm the formation of a hotspot. The flame initiated by the ignition at a hotspot propagates through the mixture at a velocity several times higher than the laminar flame speed characteristic of the mixture. The mechanism of the formation of hotspots in unsteady vortex flows and their possible effect on explosion risk assessment in some practical situations are discussed.

The replacement of hydrogen atoms by deuterium in hydrogen bonds of base pairs AT and GC decreases the rate of unwinding DNA by more than 30% per each unzipped base pair. In active helicases this isotope effect refers to the ratio of the rate constants for unzipping closed base pairs in protiated and deuterated DNA. In passive helicases the effect is controlled by ratio of equilibrium constants for opening and closing base pairs in protiated and deuterated DNA. Hydrogen/deuterium isotope effects on the unwindening of double strand DNA seems to explain, at least partly, biological and pharmacological effects of heavy water on living organisms and may be used as a means to explore new facets of the helicase functioning.

The heat-induced loss of plasticizer from and dehydrochlorination of poly(vinyl chloride) plasticized with dioctyl phthalate is studied by thermogravimetric analysis, IR spectroscopy, and colorimetry. Specific features and general regularities of the processes at high (200–320°C) and medium (100–132°C) temperatures are established. It is shown that the dehydrochlorination and oxidation processes dominate in confined space whereas, in unconfined space, plasticizer is lost largely through evaporation. The activation energies of the initial stages of the processes are determined.

In this research, the effects of interaction cyanide ion (CN⁻) with the pristine and Ge-doped aluminum phosphide nanotube (AlPNTs) are investigated using density functional theory (DFT). At first step all considered configuration models are optimized at the B3LYP/6-31G(d) level of theory. From optimized structures the structural, electrical, NMR parameters, quantum descriptors such as global hardness, global softness, electrophilicity, gap energy, Fermi level energy, electronic chemical potential, electronegativity, natural bond orbital (NBO) and molecular electrostatic potential (MEP) of all models are calculated and results are analyzed. The negative values of E_ads reveal that the adsorption process of all models are exothermic, physisorption energetically favored, and spontaneous. Inspections of results demonstrate that the adsorption of CN⁻ on the exterior surface of pristine AlPNTs is stronger than on the exterior surface of Ge-doped AlPNTs. The NBO results indicate that the E⁽²⁾ values of interaction between of (σ_Al−P) as donors and some σ* or n* orbitals as acceptors orbital at the all Ge-doped models are lower than those pristine models. The MEP results indicate that the positive potential is localized on Al atoms and it seems that these atoms are suitable sites for nucleophilic attack of CN⁻.

The results of studies of the dependence of the daily electron concentration at maximum of the F2 ionospheric layer in January 2008–2015 on the solar and geomagnetic activity are presented. The solar radio emission flux density indices F_10.7 and geomagnetic activity indices A_p were averaged over 27 days, and 〈F_10.7〉₂₇ and 〈A_p〉₂₇, respectively, were obtained. Based on the data of three stations, 27-day median (with the middle of January 15) daily N_mF2 variations were obtained for 2008–2015. Based on these data, the following paradox was discovered: in January 2014, when the values of the solar activity index F_10.7 were larger than in 2015, the dailyN_mF2 values were smaller. Averaging over four hours of local daytime (10:00–14:00 LT) gave the daily average January 〈N_mF2〉 values for each selected station for each year. To solve this paradox, a double linear regression of 〈N_mF2〉 on 〈F_10.7〉₂₇ and 〈A_p〉₂₇ was constructed. Due to this, it was concluded that the contribution of geomagnetic activity to daily January 〈N_mF2〉 values is positive. A comparison of the mean square errors of the linear and double linear regressions for 〈F_10.7〉₂₇ and 〈F_10.7〉₈₁ showed that the use of 〈F_10.7〉₂₇ led to smaller errors than the use of 〈F_10.7〉₈₁.

Results of observations of atmospheric and ionospheric parameters during the solar eclipse of March 20, 2015 have been described. The observations have been conducted by lidar sensing in the lower atmosphere and analysis of the total electron content (TEC) in the ionosphere in Kaliningrad. Observations at the troposphere altitudes have been conducted using an atmospheric lidar. Ionospheric parameter TEC has been determined according to observations of navigation satellite signals. The spectral analysis of the monitored parameters during the solar eclipse has shown that, in the lower atmosphere and the ionosphere in a period range of 2–20 min, internal gravity waves (IGWs) and infrasonic waves are excited. During the main phase of the eclipse, the major contribution to variations in the parameters of the medium comes from infrasonic vibrations. Changes in the variations in the atmospheric and ionospheric parameters with IGW periods are observed only in the initial and final phases of the eclipse.

The problem of using the direct variational method was considered for seeking all possible types of solutions to the problem on the propagation paths of shortwave radio waves in the model ionosphere with given boundary conditions. An express analysis procedure was described, which makes it possible to study the radio beam functional based on the dependence of the optical path on the shape of the chosen trajectory. As a medium for numerical calculations, a two-dimensional isotropic model of the ionosphere was used, where the electron concentration profile was given in the form of a parabolic layer. The potential of express analysis for automatic determination of radio path types was demonstrated. The fundamental difference between the upper and lower ionospheric rays and prospects for using the direct variational method for their determination were discussed.

A one-route four-step chemical reaction mechanism with three independent intermediate substances is found, the nonstationary model of which describes chaotic oscillations within the framework of the law of mass action. Numerical simulations are carried out to confirm the chaotic behavior of this reaction.

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ACKNOWLEDGMENTS

This work was supported by the Ministry of Science and Education of the Russian Federation (grant no. 14.576.21.0053 of 20.10.2014; unique identifier of applied scientific research RFMEFI57614X0053).