Polymerization of acetylene and its monosubstitutes in the presence of halides and oxohalides of molybdenum and tungsten

MoCl₅, WCl₆, and OMoCl₄ were found to be effective initiators for the polymerization of acetylene and its monosubstituted derivatives RC?CH. The polymerization proceeded in homogeneous and heterogeneous media and was carried out in nonpolar (chloroalkanes, aromatic hydrocarbons) and polar (THF, acetone, dioxane, carboxylic acids) solvents to give a high yield of polymers.     

Coherent population trapping spectra in presence of ac magnetic fields

Experimental and theoretical investigations are reported on the effects induced by an alternating magnetic field on coherent population trapping resonances. We show that the ac magnetic field produces sidebands of these resonances in such a way that the spectrum observed is similar to those observed via the FM spectroscopic technique. Because of the very narrow linewidth of the resonances, sidebands are resolved even for ac field frequencies as low as a fraction of a kHz. The theoretical model developed, which takes into account a very simple atomic structure, fits the experimental data quite well.     

Multigrid method for solving convection-diffusion problems with dominant convection

A modification of the multigrid method for the solution of linear algebraic equation systems with a strongly nonsymmetric matrix obtained after difference approximation of the convection-diffusion equation with dominant convection is proposed. Specially created triangular iterative methods have been used as the smoothers of the multigrid method. Some theoretical and numerical results are presented.     

Spin waves in cold gases with nondegenerate levels

The existence of spin waves of a new type is predicted for ultracold paramagnetic gases with nondegenerate energy levels. The waves are generated by creating a nonequilibrium population in the absence of external polarization and are damped not only by diffusion, but also by a previously ignored mechanism due to level splitting. Theoretical calculations are in fair agreement with experimental observations of spin waves in magnetically trapped clouds of rubidium atoms.     

Nuclear resonant reflectivity data evaluation with the “REFTIM” program

The program REFTIM calculates and fits the time spectra of the nuclear resonant reflectivity for given grazing angles, the prompt and delayed reflectivity curves for any multilayer structure containing ⁵⁷Fe, ¹⁴⁹Sm, ¹⁵¹Eu or another Mössbauer nuclei with M1 transitions. The program is effective if you have a set of different kind of measured data for simultaneous fit.