The objective of the research effort is to achieve detailed understanding of the excitation mechanisms operative in the xenon and helium-xenon gas lasers. The BatesDamgaard lifetime estimates were extended to include eleven different sets of xenon levels as well as four sets of neon levels. The upper laser levels in xenon i.e. the 5d levels are predicted to have extraordinarily long lifetimes. Eighteen known helium cross-sections and the two presently available for xenon, were carefully examined and certain general properties noted. Combining the results of the lifetime and cross-section considerations, a general explanation for the properties of a dischargeexcited laser system was developed. Instabilities in the plasma observed during the course of Langmuir probe studies were identified with running striations. The clean-up of xenon has been studied. Short term stability with respect to the xenon pressure was obtained by deliberately saturating the walls with xenon.