Optical spectroscopy and electronic structure of compounds HoNi5 − x Al x (x = 0, 1, 2)

The optical properties of the compounds HoNi_{5 ? x} Al _x (x = 0, 1, 2) have been investigated using the ellipsometric method in the wavelength range from 0.22 to 16 μm. The electronic structure of these intermetallic compounds has been calculated in the local electron-spin density approximation with the correction for strong electronic interactions in the 4f shell of the holmium ions. The experimental dispersion dependences of optical conductivity in the region of interband light absorption have been interpreted based on the results of the calculation of the electron density of states. The plasma and relaxation frequencies of electrons have been determined.     

Extension theorems for Stokes and Lamé equations for nearly incompressible media and their applications to numerical solution of problems with highly discontinuous coefficients

We prove extension theorems in the norms described by Stokes and Lamé operators for the three‐dimensional case with periodic boundary conditions. For the Lamé equations, we show that the extension theorem holds for nearly incompressible media, but may fail in the opposite limit, i.e. for case of absolutely compressible media. We study carefully the latter case and associate it with the Cosserat problem. Extension theorems serve as an important tool in many applications, e.g. in domain decomposition and fictitious domain methods, and in analysis of finite element methods. We consider an application of established extension theorems to an efficient iterative solution technique for the isotropic linear elasticity equations for nearly incompressible media and for the Stokes equations with highly discontinuous coefficients. The iterative method involves a special choice for an initial guess and a preconditioner based on solving a constant coefficient problem. Such preconditioner allows the use of well‐known fast algorithms for preconditioning. Under some natural assumptions on smoothness and topological properties of subdomains with small coefficients, we prove convergence of the simplest Richardson method uniform in the jump of coefficients. For the Lamé equations, the convergence is also uniform in the incompressible limit. Our preliminary numerical results for two‐dimensional diffusion problems show fast convergence uniform in the jump and in the mesh size parameter. Copyright © 2002 John Wiley & Sons, Ltd.     

Radical Processes in the Low-Temperature Radiolysis of Liposome Dispersions

Processes occurring with the participation of radiolytic radicals in the low-temperature radiolysis of aqueous liposome dispersions were studied. The initial radiation-chemical yields of the resulting radicals were determined, and the transformations of these radicals upon freezing-out the systems were examined. It was found that ionol (2,6-di-tert-butyl-4-methylphenol) introduced into the lipid bilayer of liposomes is an effective scavenger of radiolytic species formed in a frozen (77 K) dispersion upon irradiation.     

Diffractive optical elements and quasioptical schemes for experiments on a high-power terahertz free-electron laser

We have developed reflective diffraction optical elements (DOE) for focusing monochromatic coherent radiation of 400 W terahertz Novosibirsk free-electron laser (FEL). Operational characteristics of two modifications of the refractive kinoform lenses were studied. Quasioptical Toepler system with terahertz radiation recording by a thermosensitive luminescent screen was fabricated for the examination of film and solid deformation. A system for real-time terahertz radioscopy of objects with image recording with a microbolometer matrix (MBM) was fabricated. Images of objects illuminated with a plane wave or diffuse radiation were studied with the MBM. It was shown that the speckle pattern, which appears in the second case, can be averaged by means of the scatterer rotation.     

Spectral composition of the pulse generation of the N2 molecule in the3Πg(B)→3Σ11 +(A)transition

New lines in the infrared generation spectrum of molecular nitrogen are reported. The generation lines are attributed to the vibrational-rotational transitions of the first positive system of nitrogen. The distinctive features of the generation spectrum are interpreted within the framework of the direct electronic collision hypothesis. Excitation of the rotational structure is considered on the basis of a simplified model which affords qualitative agreement with the experimental data.The author is grateful to Profs. V. I. Malyshev, I. I. Sobel'man, and G. G. Petrash for their useful comments. He is also deeply indebted to the late Prof. P. A. Bazhulin for his assistance and support in the phase of the study involving pulse-generating gas lasers.     

Laser isotope separation of carbon by multiple IR photon and subsequent UV excitation of CF3I molecules

A new approach to laser isotope separation is considered. It is based on collisionless multiple photon ir laser excitation and subsequent uv laser dissociation of vibrationally excited molecules. TEA CO₂ and excimer XeF, XeCl lasers are used for ir excitation and uv dissociation, respectively. The products of photolysis (C₂F₆) are enriched with¹²C.