Laser ablation from Lithium niobate

Received: 21 May 1997/Accepted: 4 July 1997     

Numerical modeling of a XeCl laser excited by microwave discharge

12 , 169 (1987). Reasonably good agreements in the peak output power and laser efficiency have been achieved. Model calculations also predict that an efficiency as high as 2.7% can be obtained once the conditions of the above-mentioned experiments have been optimized. From the consideration that the skin depth effectively limits the absorption length of the microwave pumping and hence the excitable volume, it is concluded that high input power densities (>2 MW/cm³) and higher gas pressures (between 3 and 10 atm) are the preferable conditions to achieve higher efficiency. Preliminary calculations on CCl₄ containing XeCl gas mixtures show that improvement in laser efficiency by several folds may be achieved as a result of the higher intrinsic efficiency of excimer formation. Received: 23 September 1996 / Revised version: 25 March 1997     

Determination of the largest lyapunov index for short chaotic time sequences in self-oscillating chemical reactions

A method was developed for the determination of largest Lyapunov index for short chaotic time sequences with allowance for the presence of noise in the response of the system. For this purpose a simple unidimensional representation modelling the dynamics of irregular self-oscillations was investigated. Conditions were found for adequate determination of the largest Lyapunov index from the noise-distorted signals. The results were used to obtain the largest Lyapunov index for the Belousov—Zhabotinskii reaction taking place in an ideal-mixing closed reactor and in a constant-mixing flow-type reactor. Institute of Organic Chemistry, National Academy of Sciences of Ukraine. Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 33, No. 3, pp. 136–142, May–June, 1997.     

Influence of the domain structure on the permeability of planar hexaferrites in the natural ferrimagnetic resonance region

A calculation is presented of the permeability of hexaferrites with an easy magnetization plane in the region of natural ferrimagnetic resonance and in the presence of a domain structure. It is shown that the domain structure strongly influences both the magnitude of the permeability and the natural ferrimagnetic resonance frequency. The expressions obtained are compared with the results of calculations of the natural ferrimagnetic resonance spectra of single-domain planar hexaferrites. State University, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 53–57, February, 1997.     

Pseudoparabolic variational inequalities without initial conditions

We consider a pseudoparabolic variational inequality in a cylindrical domain semibounded in a variable t. Under certain conditions imposed on the coefficients of the inequality, we prove theorems on the unique existence of a solution for a class of functions with exponential growth as t → ∞. Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 50, No. 7, pp. 919–929, July, 1998.     

Criteria for controllability and observability in complex domain models of stationary systems

We propose criteria for controllability and observability of stationary systems specified by complex domain models. Conclusions concerning controllability and observability are made on the basis of coefficients in the corresponding transfer functions. Translated fromDinamicheskie Sistemy, Vol. 12, pp. 120–126, 1993.     

Asymptotic behavior of neutron small-angle multiple scattering spectra

The asymptotic behavior of the spectra for large values of the scattering vector for the case of elastic multiple small-angle neutron scattering (SANS) is investigated theoretically and experimentally. An expansion of the spectrum in terms of the reciprocal of the magnitude of the momentum transfer is obtained taking account of the influence of the instrumental line. It is shown that, to within some factor, the leading term of the expansion is identical to the differential single-scattering cross section averaged over a statistical ensemble of particles; several subsequent terms in the expansion are calculated and the range of applicability of the resulting expressions is determined. The asymptotic behavior of the multiple SANS spectrum is measured, using a two-crystal neutron spectrometer, for samples of an HTSC ceramic, the alloy Fe-Ni, and Al powder. The agreement between the experimental results and the theoretical predictions is analyzed. Zh. éksp. Teor. Fiz. 114, 2194–2203 (December 1998)     

Influence of composition and annealing on the criteria of superparamagnetism and the interaction of particles in granular electrolytically deposited films of CuCo

Films of nonuniform Cu_100−xCo_x alloys with x = 6, 11, 20, and 35 at. %, obtained by electrolytic deposition, are investigated using quantum magnetometry in fields of up to 5.5 T and temperatures of 2–300 K. In all the compositions a characteristic feature is the deviation from pure superparamagnetic behavior, which increases as the annealing of the films and their cobalt content increase. Institute of Solid State and Semiconductor Physics. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 60–62, March, 1998.     

Scattering of polarized electromagnetic radiation by turbulent fluctuations of a high-temperature plasma

An investigation was made of the process of Raman scattering of polarized electromagnetic radiation by turbulent fluctuations in a plasma with a magnetic field. It was found that a turbulent plasma with a magnetic field scatters left- and right-handed circularly polarized radiation in different ways. The possibility is analyzed of using the results obtained in order to provide diagnostics for different plasma characteristics in thermonuclear fusion devices employing magnetic plasma confinement. Institute of Solar and Terrestrial Physics, Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 102–107, April, 1998.