Energy and angular momentum transfer in atom-diatom collisions from polarized laser fluorescence

We report a study of collisional reorientation of diatomic lithium molecules by rare gas atoms using high resolution circularly polarized laser fluorescence. As in the case of I2 we find that elastic collisions are very inefficient at reorienting Li2 molecules and a selection rule ΔM′ J = 0 appears to be in operation. Rotationally inelastic collisions, particularly those with argon, cause some degree of reorientation and are the result of relatively long range intermolecular interactions. Vibrational transfer features are more strongly depolarized. Optical pumping studies of oriented 1Σ g Li2 molecules have yielded a cross section for inelastic transfer of 35 ± 15 Å2.