The covalent and ionic states of the rare gas monofluorides

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Abstract
Ab initio configuration interaction calculations have been carried out on the electronic states of RgF (Rg=Ne, Ar, Kr, and Xe) arising from the covalent, Rg(1S)+F(2P), and ionic, Rg+(2P)+F−(1S), separated atom limits. Spin–orbit effects, which have been shown to be important in the ionic states, are included in a semiempirical manner. The potential curves of all of the covalent states were found to be repulsive while those of the ionic states were strongly bound (De∼5–6 eV). Only those transitions for which ΔΩ=0 were found to be strong. The intense laser emissions at 193 nm in ArF, 248 nm in KrF, and 352 nm in XeF all arise from a transition between the lowest ionic Ω=1/2 state and the lowest covalent Ω=1/2 state (III1/2–X1/2 in our notation). The calculated lifetimes of the III1/2–X1/2 laser transition varies from 2.6 nsec (NeF) to 12 nsec (XeF).