Charge-Transfer Excitation ofAr+in Low-EnergyHe++ Ar Collisions

An experimental study has been made of the excitation of the ArII spectrum in low-energy (10-1000 eV) ${\mathrm{He}}^{+}$ + Ar collisions. The principal states excited, which have lines from 3500 to 5200 Å, have been positively identified. The dependence of excitation on energy has been measured for six states. It is found that states with ${}_{}{}^1{}_{}{}^{}D$ parent terms are generally stronger and have more rapid rise with energy at threshold than states with ${}_{}{}^3{}_{}{}^{}P$ parent terms. The effect of cascade from higher excited states on the intensities of the strongest lines has been studied. The energy dependence of one state is compared with the form expected from a simple Landau-Zener model.