Polarizability of interacting atoms: Relation to collision-induced light scattering and dielectric models

Abstract

The polarizability tensor of a pair of interacting He atoms has been calculated as a function of internuclear separation r using the fully self-consistent Hartree-Fock theory. It was found that the trace of the polarizability tensor, α(r), to which the second dielectric virial coefficient Bε is directly proportional, decreases with decreasing r, giving a theoretical value of Bε=-0.093 a.u. at room temperature, compared with the experimental result Bε=-0.06±0.04 a.u., measured by Orcutt and Cole [J. Chem. Phys. 46, 697 (1967)]. This is the first calculation that predicts the correct sign of Bε. We conclude that for He the effects of overlap are of opposite sign from and of sufficient magnitude to overcome the contributions of the van der Waals interaction to α(r). Furthermore, the anisotropy of the pair polarizability β(r) can be represented by a simple form: β(r)=6α2r-3-λ e-r/r0, where r0=0.74 a.u., and the collision-induced light-scattering spectrum predicted by this form has an essentially exponential line shape. These results are in qualitative agreement with recent work on collision-induced light-scattering spectra from rare gases.