Asymmetric rearrangement collisions: VUV emission spectra in keV He and Ne ion-atom collisions with Ar

Abstract
The authors report observations of vacuum ultraviolet spectra from He+ and Ne++Ar single collisions and the inverse collisions Ar++He, Ne in the 500 to 1100 AA range, and energy range 8-30 keV. Comparison is made with available theory for excitation of the Ar+ 920-932 AA doublet, involving two-state and four-state quasimolecular calculations with and without electron translation factors. None of the simple theoretical calculations available fits the shape of the data accurately, but the data suggest that a refined two-state theory incorporating electron translation factors may give reasonable agreement in the He++Ar case. The large cross section near 2 keV amu-1 for Ar II 920-932 AA doublet excitation in a rearrangement collision with He+ implies a possible ion-beam-pumped VUV laser candidate.