Generation of mesoscopic magnetic structures by local laser action

New effects are observed wherein the internal structure of the domain walls in a thin magnetic iron garnet film are modified by the action of focused laser radiation. A single laser pulse with increasing power gives rise to the following: 1) displacement of vertical Bloch lines in a domain wall; 2) generation of a pair of vertical Bloch lines on initially line-free walls; and, 3) an irreversible change in shape of a domain wall and the domain structure as a whole. The mechanism leading to the generation and displacement of Bloch lines is connected with the motion of domain walls which is induced by a local change in the distribution of demagnetizing fields as a result of a heating-induced decrease of the magnetization in the focal spot of the laser radiation. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 6, 398–402 (25 September 1997)     

Self-energy correction to the hyperfine splitting of the 1 s and 2 s states in hydrogenlike ions

The one-loop self-energy correction to the hyperfine splitting of the 1 s and 2 s states of hydrogenlike ions is calculated for both point and finite nuclei. The results of the calculation are combined with other corrections to find the ground state hyperfine splitting in lithiumlike ²⁰⁹Bi⁸⁰⁺ and ¹⁶⁵Ho⁶⁴⁺. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 1, 19–22 (10 July 1997) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Luminescence properties of anodic aluminum oxide films with organic luminophores embedded into pores

Luminescence properties of porous anodic aluminum oxide films formed in a 0.6 M solution of citric acid and luminescence of paraterphenyl, perylene, coumarin 7, and rhodamine 6G dyes adsorbed by the films are investigated. The nature of emitting centers in anodic aluminum oxide is revealed. Intense photoluminescence of all tested dyes embedded into pores of anodic aluminum oxide has been found. A redshift of fluorescence spectra of dyes adsorbed by the matrix and emergence of an additional longwave band have been detected. Data obtained can be used in developing new thin-film luminescent coatings for future applications in optoelectronics and molecular electronics. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No 4, pp. 483–488, July–August, 1997.     

High power CW solid-state multilaser system

A laser system containing four CW Nd:YAG double-rod lasers, transforming optics and a fibre with input-output optics has been designed and investigated. It is shown that reduction of the beam parameter product of the non-Gaussian beams in the image space of the lens has made it possible to collect the emission of four lasers to the same fibre. Independent laser operation has provided the output power control in the range of 10–900 W with a stable light spot size on the input end of the fibre.     

Experimental study of the emission spread at gyrotron cathodes by current-voltage characteristics

A scheme for automated study of current-voltage characteristics of gyroresonance devices is developed. The effective emission spread at the cathodes of powerful gyrotrons is studied by analysis of current-voltage characteristics. Experimental data on the effective emission spread parameter for different modes are given. The permissible emission spread at the cathodes of powerful gyrotrons is estimated, and the dependence of the electron beam parameters on the cathode emission spread is presented. A complex measurement technique showing the contribution of different physical mechanisms to the cathode emission spread is proposed. Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 4, pp. 506–516, April, 1997.     

Phase shift moiré studies of processing-induced residual strains in Nickel 200 spot welds

Processing-induced residual strains in solid cylinders of Nickel 200 were investigated using phase shifting moiré interferometry. Two different experimental approaches were used to study the strains produced during Tungsten-inert gas spot welding. A comparison of results for a ‘hot/fast’ and a ‘cool/slow’ weld demonstrate the capabilities of the general approach. Both experimental methods revealed distinct differences in the residual displacement and strain fields between the two types of welds.     

Dissipative Nonlinear Evolution Equations and Chaos

In this article we have studied the nonlinear interaction between ellipticity and dissipation in a set of model equations (1.1) and established the relation between this interaction and chaos. In addition to theoretical investigations, extensive numerical simulations with these equations have been made, and different routes to chaos have been found. The numerical studies have revealed the chaotic nature of the solutions.     

Fischer--Tropsch, hydrotreating and superClaus catalysts

In modern society the application of catalysts, and hence, research in the field of catalysis, is becoming more and more important. In the strongly increasing chemical industry most reaction processes are performed with the aid of catalysts. Knowledge about the structure of the active sites present at the surface of catalysts will facilitate the design of new catalysts with better performances. Such knowledge can be obtained by Mössbauer spectroscopy, which is an excellent in-situ characterization technique due to the high penetrating power of the γ-radiation used and the sensitivity of the spectral parameters for the chemical state and local environment of the Mössbauer atoms.