Long-range interactions of alkali metals

Abstract

The leading term in the long-range interaction energies between pairs of alkali metal atoms and between alkali metal atoms and inert gas atoms are computed from optical data; while the contribution from the continuum is negligible, it is suggested that the contribution from inner shell transitions may be substantial. The results for alkali metal-inert gas pairs are in harmony with atomic beam elastic scattering measurements but those for alkali metal-alkali metal pairs are not. It is shown that the discrepancies cannot be attributed to a failure of perturbation theory but that they are due probably to the persistence at large distances of the first-order forces in the singlet and triplet molecular states.