Hydrodynamic, conformational, and optical properties of cellulose tridecanoate molecules in solutions

Cellulose tridecanoates of various molecular weights were synthesized, and their characteristics in chloroform and tetrachloroethane solutions were studied by methods of translational diffusion, velocity sedimentation, flow birefringence (Maxwell’s method), and viscometry. The effects of solvent and temperature on the conformational characteristics of the macromolecules under consideration were examined. The anisotropy of the monomeric unit of cellulose tridecanoates was studied, and the contribution of pendant chains to the optical anisotropy of macromolecules of cellulose esters with aliphatic substituents was analyzed.     

Suppression of the polarization bremsstrahlung from a fast charged particle in an amorphous medium

Based on a consistent quantum-mechanical approach, we calculate and analyze the suppression of the polarization bremsstrahlung (PB) from a fast charged particle moving in an amorphous medium. The suppression effect is attributable to destructive interference between the contributions from atoms of condensed material to the bremsstrahlung due to their finite sizes and chaotic arrangement. We calculate the spectral and angular PB dependences on various targets that demonstrate characteristic features of the phenomenon under consideration. We have established the region of the clearest manifestation of the suppression effect. The results obtained by various methods of calculation are compared.     

Elastic Scattering of Ultrashort Laser Pulses on Noble Gas Atoms

Russian Physics Journal - The work deals with a theoretical investigation of elastic scattering of ultrashort electromagnetic pulses (USP) on the noble gas atoms in the far ultra-violet and soft...     

Excitation of a hydrogen atom by bichromatic radiation with the frequency ratio 1:2 in the presence of electric field

In the framework of perturbation theory, a probability of excitation of a hydrogen atom from the ground to the first excited state under bichromatic laser radiation with the frequency ratio 1:2 in the presence of electric field is calculated, taking into account quantum interference of two process channels. In the case under study, a coherent superposition of the 2s-and 2p-states, necessary for quantum interference to occur, is formed under the action of the external electric field. The excitation probability is analyzed depending on the relative phase of monochromatic radiation components (the coherent phase control) for two extreme cases: for a strong electric field, where the Stark splitting of an upper level essentially exceeds the spin-orbit one, and for the contrary limit of a weak field. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 20–28, August, 2006.     

Nonlinear surface photoeffect in multi-color laser field: effect of the finite width of the surface potential barrier

Received: 20 September 1998     

Bremsstrahlung spectrum of nonrelativistic electrons scattered in metallic target: Theory and experiment

This work is devoted to theoretical and experimental investigation of the bremsstrahlung (BrS) spectrum of electrons with an energy of 10–30 eV scattered in a copper plate. Modeling of the photon yield from a target has been carried out taking into account the polarization BrS channel, elastic and inelastic electron scattering by medium atoms, photon absorption in the target material, and coherent effects when electrons interact with a polycrystalline structure of metal. An FEI Quanta 200 scanning electron microscope with a supplement for X-ray microanalysis was used. Good agreement between experimental and theoretical results has been obtained.     

Statistical Models in Theory of Polarization Bremsstrahlung

Universal relations have been derived to describe the spectral-angular dependence of the polarization bremsstrahlung of a fast charged particle, based on a statistical model for the electron skeleton of the target. Three statistical atomic models are considered in terms of which the target characteristics that determine the cross section for polarization bremsstrahlung are calculated and analyzed.