Investigation of a microwave discharge in argon/helium mixtures

The role of helium in obtaining a laser effect during continuous microwave discharges with 50-50 argon/helium mixtures was studied. Empirical relations between the intensity of rays emitted by the plasma, electron density, and the average plasma electric field were established. For argon 1, the excited levels are populated by electron collisions in one step from the base of the atom. For helium 1, population of upper levels of transitions is accomplished in two stages, via a metastable step. For argon 2, the excited layers, especially the upper laser levels, are populated by electron collisions in three stages via the fundamental ion state and the metastable argon ion. The three stage process dominates argon lasers with the best output. The role of helium is shown by a change in the field exponent in relation to argon 2 intensity, which results from a change in the electron distribution function following ionization.