Charge transfer into excited states in thermal energy collisions

Abstract

Flowing afterglow techniques are employed for the study of the thermal energy reactions of He⁺ with Zn, Cd, and Se, and of Ne⁺ with Mg. The He⁺ reactions have a practical importance as excitation mechanisms in the He-Zn; He-Cd and He-Se laser systems. The degree to which excited states of the metal ion closest to the rare gas ionization energy are preferentially populated in the formation process is investigated. Relative reaction rates are deduced from measurements of the emission line intensities with the aid of calculated transition probabilities. The largest reaction rates are found to be those for levels of the product ion lying some 0.1-0.4 eV below exact resonance. Such behaviour is shown to be consistent with the predictions of a semi-empirical 'curve-crossing' model of the ion-atom interaction.