The effect of collisions on the rotational angular momentum of diatomic molecules studied using polarized light.

We report results of an experimental study of the changes in the alignment of the rotational angular momentum of diatomic molecules during elastic collisions. The experiment involved collisions of diatomic lithium molecules in the A1Σu + excited electronic state with noble gas atoms (helium and argon) in a thermal gas phase sample. Polarized light for excitation was combined with the detection of polarization-specific fluorescence in order to achieve magnetic sublevel state selectivity. We also report results for rotationally inelastic collisions of Li2 in the lowest lying rotational levels of the A1Σu +v=5 vibrational state with noble gas atoms.