The covalent and ionic states of the xenon halides

The electronic states and spectroscopic properties of the xenon halides, XeX (where X=F, C1, Br, I), are characterized on the basis of ab initio configuration interaction calculations. States dissociating to Xe(1S)+X(2P) and Xe+(2P)+X−(1S) are treated, and the effects of spin-orbit coupling are introduced in a semiempirical atoms-in-molecules model. The intense laser emissions in XeF (353 nm), XeC1 (308 nm), and XeBr (283 nm) and the strong fluorescence in XeI (253 nm) arise from a transition from the lowest Ω=1/2 state to the lowest covalent 1/2 state (III1/2→I1/2 in our notation). The calculated lifetimes for these transitions are all 11–12 nsec. Four other major emissions with ΔΩ=0 are predicted for each XeX species.