Spatial macroscopic structure of a pulsed microsecond discharge in barrier-metal gaps with a nonuniform electric field distribution

Electric and spatial characteristics of a pulse-periodic microsecond barrier discharge are investigated in different geometries—triangular prism, plate, and corrugated electrode—that are in contact with a dielectric plate and form a dihedral angle with it. It is established that, in the space of the dihedral angle, the regions of discharge represent alternating cylindrical layers with the axes lying on the contact line. The first conducting layer is formed at some distance from the contact edge of the electrode. The number of layers and their localization are determined by the angle formed between an electrode and the dielectric plate. A physical model explaining the main features of the structure formation is proposed.     

Photophysical properties of carborane-containing derivatives of 5,10,15,20-tetra(p-aminophenyl)porphyrin

Absorption, fluorescence emission, fluorescence excitation spectra and fluorescence decay kinetics of carborane derivatives of 5,10,15,20-tetra(p-aminophenyl)porphyrin have been investigated. Carborane derivatives are prepared by acylation of the amino groups of 5,10,15,20-tetra(p-aminophenyl)porphyrin by 9-carboranyl acetyl chloride. From the analysis of the absorption and fluorescence spectra, it is concluded that covalent linking of carborane molecules to the tetraphenylporphyrin molecule significantly changes the self-conjugated pi-system of the porphyrin macrocycle: positions of maxima of absorption and fluorescence spectra shift to the red region by 3-8 nm; the halfwidths of these bands are broadened by 2.5-5.0 nm; the relative intensity of the bands I-IV also changes. The fluorescence decay kinetics of the carborane derivatives are biexponential. According to the experimental data and model simulation, it is concluded that the intramolecular electron transfer proceeds from the porphyrin excited part of the molecule to carboranyls with a rate constant of 415 ps(-1) and efficiency of 0.16-0.8. Recombination of separated charges occurs within 1.4 ns.     

Microwave radiation absorbers based on corrugated composites with carbon fibers

A complex analysis of the dependence of the absorption coefficient of polymer composites with nonmagnetic carbon inclusions on the real and imaginary parts of the complex permittivity, as well as on the material thickness is performed in frequency range 26–37 GHz. The composites containing 0.2 wt % of carbon fibers have been obtained. It has been experimentally found that the corrugation of the composite surface substantially increases the absorbability (from 63 to 92% at a frequency of 30 GHz and a thickness of 4.50 mm) upon a decrease in the sample mass (by 28%). A method has been proposed for calculating the absorptance of corrugated composites in the microwave range.     

Lie algebras in quantum optics and molecular spectroscopy

We briefly review some applications of dynamical Lie algebras and groups and their associated coherent states in quantum optics and molecular spectroscopy.     

Non-markovian relaxation models in the theory of radiation of two-level atoms

The short-memory processes in a system consisting of two dipole-dipole interacting atoms have been theoretically investigated. The radiation line profile is constructed, and the possibility of detecting memory effects in radiation spectra is discussed.     

Acylation of Meldrum’s acid with arylacetic acid imidazolides as a convenient method for the synthesis of 4-aryl-3-oxobutanoates

C-Acylation of Meldrum’s acid by (het)arylacetic acids in ethanol in the presence of 1,1′-carbonyldiimidazole leads to ethyl 4-(het)aryl-3-oxobutanoates in high yields.     

Resonance photons in a gravitational radiation field and the regularization problem for the energy-momentum tensor

The exact solutions of the relativistic kinetic equation for a photon gas subjected to the influence of a relativistic fluid and a gravitational radiation field are analyzed. Singular solutions describing resonance and entrained photons moving at a gravitational wave front are investigated. The problem of the divergence of the energy-momentum tensor in models admitting resonance photons is discussed.V. I. Ul'yanov (Lenin) State University, Kazan. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 70–75, October, 1994.