Waveguide propagation of intense electromagnetic radiation in slightly inhomogeneous nonlinear media

The propagation of self-localizing beams of electromagnetic waves in the form of nonlinear waveguides in a slightly inhomogeneous medium is studied analytically and numerically. The trajectories of the axial ray are studied as a function of its direction and the field strength at the initial point on the basis of a nonlinear scalar Helmholtz equation. Analytic expressions are derived. The longitudinal refractive index, the field intensity, and the waveguide radius are plotted as functions of the instantaneous position of the point on the axial ray. Deep penetration of the beam into the opaque region and the position of the screening surface are studied as functions of the parameters of the beam and the medium. A steady-state 3D problem is analyzed for a power-law nonlinearity with an arbitrary power. A 2D problem is analyzed for the case of a ponderomotive nonlinearity with saturation.     

Influence of the adsorption potential on the composition of formaldehyde chemisorption products on platinum

The influence of the adsorption potential on the composition of formaldehyde chemisorption products on platinum has been investigated by the radioactive tracer method in conjunction with electrochemical methods. It is shown that in the potential range 0.0–0.3 V the main adsorption product of formaldehyde is a particle of composition COH, and at the potential 0.4 V a particle of composition CO. It has been found that at E<0.3 V adsorbed CO particles are reduced to COH particles. The electrochemical properties of these particles have been studied.     

Oxidation of 2,4-Dinitrotoluene with an Ozone-Oxygen Mixture

Oxidation of 2,4-dinitrotoluene to 2,4-dinitrobenzoic acid with an ozone-oxygen mixture in glacial acetic acid was studied.     

Molecular and Electronic Structure of Trimethylsilylpropiolamides

The specific features of molecular and electronic structure of trimethylsilylpropiolic acid amides were studied by means of IR spectroscopy and quantum chemistry (AM1). The competition between p,-conjugation in the amide fragment and ,-conjugation in the ethynylcarbonyl group CC-C=O was established. The prevailing conformers were revealed, their geometrical parameters were established, the barriers to internal rotation around the amide C-N bond were calculated for acyclic (13 kcal mol^-1) and heterocyclic (8.12 kcal mol^-1) amides.     

Interaction of oxygen with complex of cobalt (II)-bisalicylal-o-phenylendiamine with pyridine fixed on the surface of silica

A complex of Co(II)-bisalicylal-o-phenylendiamine with pyridine fixed on the surface of aerosil was synthesized. Mono- and bi-pyridine complexes of Co(II)-bisalicylal-o-phenylendiamine are formed depending on the concentration of the bonded pyridine. The interaction of this complex with oxygen was studied by means of reflection spectroscopy in the UV and visible ranges, and by EPR-spectroscopy. Superoxo- and peroxodicobalt complexes with oxygen were identified.     

Influence of low-intensity electromagnetic field on autooscillations of concentration in belousov-zhabotinskii reaction

A study has been made of the influence of an electromagnetic field (EMGF) with a frequency in the 40–60 GHz range and intensity up to 4–8 mW on autowaves of concentration in the reaction of sodium bromate (0.3 M), malonic acid (0.2 M), sulfuric acid (0.45 M), and Ferroin (0.003 M). It has been found that the action of the EMGF leads to decreases in the wavelength by amounts up to 26%. The experimentally measured temperature gradient created by the EMGF in a thin layer of the reaction mixture is no greater than 0.4°K. The value calculated for the solution temperature rise that is required to create the experimentally observed decrease in wavelength is 5–6° K. It is concluded, therefore, that the observed effect cannot be explained solely by thermal action of the EMGF through heating the reaction mixture.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 6, pp. 704–709, November–December, 1989.     

Exploration of the Crystal Structure and Thermal and Spectroscopic Properties of Monoclinic Praseodymium Sulfate Pr2(SO4)3

Praseodymium sulfate was obtained by the precipitation method and the crystal structure was determined by Rietveld analysis. Pr₂(SO₄)₃ is crystallized in the monoclinic structure, space group C2/c, with cell parameters a = 21.6052 (4), b = 6.7237 (1) and c = 6.9777 (1) Å, β = 107.9148 (7)°, Z = 4, V = 964.48 (3) ų (T = 150 °C). The thermal expansion of Pr₂(SO₄)₃ is strongly anisotropic. As was obtained by XRD measurements, all cell parameters are increased on heating. However, due to a strong increase of the monoclinic angle β, there is a direction of negative thermal expansion. In the argon atmosphere, Pr₂(SO₄)₃ is stable in the temperature range of T = 30–870 °C. The kinetics of the thermal decomposition process of praseodymium sulfate octahydrate Pr₂(SO₄)₃·8H₂O was studied as well. The vibrational properties of Pr₂(SO₄)₃ were examined by Raman and Fourier-transform infrared absorption spectroscopy methods. The band gap structure of Pr₂(SO₄)₃ was evaluated by ab initio calculations, and it was found that the valence band top is dominated by the p electrons of oxygen ions, while the conduction band bottom is formed by the d electrons of Pr³⁺ ions. The exact position of ZPL is determined via PL and PLE spectra at 77 K to be at 481 nm, and that enabled a correct assignment of luminescent bands. The maximum luminescent band in Pr₂(SO₄)₃ belongs to the ³P₀ → ³F₂ transition at 640 nm.     

Role of adhesion in the metal-semiconductor phase transition in polycrystalline vanadium dioxide films

Etching of thin polycrystalline films of vanadium dioxide with hydrofluoric acid vapor has offered a possibility to reveal a significant influence of the extent of adhesion on the temperature position and shape of the hysteresis loop of the reflectivity. It has been established that, in the cases where silicon is used as a substrate, etching at room temperature is accompanied by incorporation of hydrogen into thin films of vanadium dioxide.