Knowledge Bank

Excitation of $Ar/Kr/F2$ mixtures has produced broad emission bands at 400 and 290 nm that have been assigned to $Kr2F$ and $Ar2F.1$ Large basis set configuration interaction calculations have been performed on six low-lying states of $Ar2F$ in order to elucidate the observed spectra and make definite state assignments. The six lowest states consist of three repulsive covalent states and three attractive ionic states $(Ar2+F-)$. The ionic states favor isosceles triangle geometries over linear geometries. However, only one ionic state $(22B2)$ is bound (by 0.60 eV) relative to $Ar^{+}F^{-} + $Ar. The wavelengths for the $22B2\to 12A1$ and $22B2\to 12B2$ transitions are calculated to be 268 and 274 nm, respectively, which compares favorably with experiment (290 nm). The calculated lifetimes for the two transitions are both long, 245 $ns(22B2\to 12A1)$ and 269 $ns(22B2\to 12B2)$. The implications of these results for the kinetics of ArF and KrF lasers will be considered briefly.