Abstract
Excitation processes in the positive-column helium-cadmium laser discharge are investigated using the axial dip which is apparent in the radial profiles of emission from excited cadmium states. By comparing the profiles of different states under certain discharge conditions, it is shown that electron collisions probably contribute significantly to the excitation of levels which are normally assumed to result from charge-exchange and Penning collisions. Radial profiles of helium and cadmium metastable species and the cadmium-ion ground-state population are also observed and the significance of these results in relation to accepted discharge models is examined. Results for the helium-cadmium system may be generalised for all positive-column metal-vapour system.
Keywords