Crystal nucleation and growth rates in single-component and binary melts under conditions of growth in a polycrystalline layer and in the case of single crystals

Crystal nucleation and growth rates in single-component and binary melts are found using the proposed versatile procedure for determining kinetic parameters in processes involving phase transformations. These kinetic dependences on supercooling at the interface for the same single-component and binary melts are experimentally derived under comparable conditions in the formation and growth of single crystals and in a polycrystalline layer. A discrepancy between growth rates in a polycrystalline layer (constrained conditions) and for single crystals under the same supercooling is found. The rate of nucleation under constrained conditions is also lower. In practice, when calculating the process of crystallization, it is necessary to use kinetic parameters obtained for constrained conditions of the process. In studying the mechanism of crystal nucleation and growth, kinetic parameters derived for single crystals should be used.     

Powerful electroionization laser on Xe infrared atomic transitions

A powerful pulsed high-pressure Ar-Xe laser with an active volume of 91 is studied. Laser output energies of 5.8 J for electron-beam pumping and 19 J for electroionization pumping are attained. The laser power exceeds 13 MW. More than 95 percent of the output laser energy is concentrated in the line withlambda = 1.73 mum. Efficiencies greater than 5 percent were observed.     

Momentum Defect in Impact of a Short Rod Against a Smooth Obstacle

The problem of deformation of an elastic halfplane under the effect of a finite load of special form on its boundary is studied theoretically. Using Laplace and Fourier transformations the authors obtained a finite relation for the total force on the axis of symmetry of the halfplane that is used to study momentum loss in impact of a short elastic rod against a smooth absolutely rigid obstacle. With certain limitations on the dimensions of the rod the authors obtained an accurate analytical estimate of the momentum loss that is associated with conversion of part of the energy of the striker to the energy of its transverse oscillations.