Near-ultraviolet emission bands of Li—rare-gas molecules

Abstract

Near-ultraviolet emission bands have been observed in Li-Ar, Li-Kr, and Li-Xe mixtures. The bands are due to transitions from bound molecular Li---rare-gas states associated with the atomic Li $3d$, $3p$, and $3s$ states and ground-state rare-gas atoms. The transitions are all to the dissociative Li---rare-gas $2s\ensuremath{\sigma}$ molecular ground state. The Li-Ar, Li-Kr, and Li-Xe $3s\ensuremath{\sigma}\ensuremath{-}2s\ensuremath{\sigma}$ collision-induced bands are progressively shifted, for the heavier rare gases, further to the red of the asymptotic atomic Li $3s\ensuremath{-}2s$ energy difference. For Li-Xe this shift is a remarkable 4000 ${\mathrm{cm}}^{\ensuremath{-}1}$. We also report rate coefficients for quenching, by all the rare gases, of the atomic Li $3d$ and $3p$ states.