State-selective electron capture by C2+, C3+, N2+and Ar2+ions in rare gases

Energy loss/gain spectroscopy is used to study state-selective one-electron capture by 1.6-6 keV C 2+ in He, Ne and Ar, by 0.8-8 keV N 2+ in He and Ne, by 0.14-5 keV Ar 2+ in He and Ne, and by 3-18 keV C 3+ in He. The relative contributions of the various collision product channels are determined. Moderately exothermic processes involving curve crossings at moderate internuclear separations are shown to be dominant and a strong influence of metastable ions in the primary beam is observed for some reactions. Serious discrepancies with some previous measurements are noted. The main collision channels observed are in accord with the Wigner total electron spin conservation rule.