Quasiresonant Vibration↔Rotation Transfer in Atom-Diatom Collisions

Abstract

We have performed an extensive level-resolved experimental study of vibrotationally inelastic collisions in this system ${\mathrm{Li}}_{2}^{*}({v}_{i},{j}_{i})+\mathrm{Ne}\ensuremath{\rightarrow}{\mathrm{Li}}_{2}^{*}({v}_{f}={v}_{i}+\ensuremath{\Delta}v,{j}_{f}={j}_{i}+\ensuremath{\Delta}j)+\mathrm{Ne}$, with $8\ensuremath{\le}{j}_{i}\ensuremath{\le}76$. At high ${j}_{i}$, the rate of vibrational transfer is large, exceeding the purely rotationally inelastic rate, and extremely specific, populating only a few rotational levels per $\ensuremath{\Delta}v$. The most probable $\ensuremath{\Delta}j$ obeys the rule $\ensuremath{\Delta}j=\ensuremath{-}4\ensuremath{\Delta}v$. These effects are enhanced at low collision velocity and are quite insensitive to ${v}_{i}$ and the target gas. Classical trajectory calculations reproduce these results.