Pair Polarizability of Hydrogen Atoms. Relation to Collision-Induced Light Scattering and Dielectric Phenomena in Rare Gases

The polarizability tensor as a function of internuclear separation of hydrogen atoms is calculated, using the approximate variational wavefunction for ground- and first-excited-state H2 of Hirschfelder and Linnett. Two interacting hydrogen atoms in the nonbonding triplet state have certain qualitative features in common with colliding pairs of rare-gas atoms. In particular, the system exhibits the long-range dispersion attraction and short-range overlap repulsion of interacting closed shell atoms. Results of the calculations here on 3ΣH2 are capable, in analogy, of explaining observed trends in collision-induced light scattering intensities and the second dielectric virial coefficient of rare gases, which cannot be accounted for on the basis of long-range dispersion force models or perturbation theory alone. The major source of the effect is found to be the distortion of electronic charge density at intermediate and small internuclear separations.