HELIUM SINGLET AND TRIPLET METASTABLE NUMBER DENSITIES IN HOLLOW-CATHODE-METAL-VAPOUR LASERS

Number densities of helium singlet and triplet metastable states in the hollow cathode discharge appropriate to metal vapour lasers have been measured; in particular their dependence on discharge current and pressure, cathode fall potential and cadmium partial pressure has been explored. Singlet and triplet densities behave differently with discharge parameters; whereas the former saturate with both current and pressure, the latter increase linearly with discharge current and follow the distinctive behaviour exhibited by the cathode fall potential as a function of pressure. Radial profiles of the metastable densities are also reported.