Structure and dynamics of the He-2(*) (a3 Sigma(+)(u)) molecular complex in condensed phases of helium

An investigation is made of the absorption spectra of triplet metastable he lium molecules in the a(3) Sigma (+)(u)state in liquid He-4 and He-3 at var ious pressures and in dense He-3 gas. An analysis of the spectrum correspon ding to the a(3)Sigma (+)(u) --> c(3)Sigma (+)(g) transition confirms the c onclusion that there is a microscopic bubble surrounding the molecule in li quid helium. A simple approximation is proposed for the wave function of th e valence electron of the molecule and the parameters of the bubble are det ermined for various experimental conditions. The coefficient of molecular r ecombination in liquid He-3 and He-4 was determined experimentally at vario us pressures and in dense cold He-3 gas. The results show good agreement wi th the theory of mutual recombination limited by molecular diffusion under conditions of strong van der Waals interaction. It is shown that in the con densed phases of helium the polarization of the molecules under the action of the magnetic field does not lead to suppression of their mutual recombin ation, and this is confirmed experimentally. (C) 2000 MAIK "Nauka/Interperi odica".