Relative yields of ground-state and excited-state ions of Zn, Cd and Hg in thermal-energy charge-transfer reactions of He⁺ ions

The production rates of zinc, cadmium and mercury ions in their ground states, relative to those leading to excited-state formation, in thermal-energy charge-transfer collisions with He⁺ ions have been measured in a flowing afterglow. In the cases of cadmium and mercury cross sections for ground-state production are very small compared to those for excited-ion production. Although a full analysis of the zinc system cannot yet be carried out, it is likely that a similar result will hold. The results have been explained in terms of pre-emption of the molecular curve crossings in the Landau-Zener model. From this evidence the authors conclude that the present power limitations of the helium-metal-vapour laser are not determined by atomic processes of this type.