The mechanisms of level population in high pressure gas lasers pumped by ionizing radiation at the 3p-3s transitions of neon, the d-p transitions of argon, krypton, xenon, and triplet lines of mercury are analyzed. It is shown that dissociative recombination of molecular ions with electrons is not the basic process responsible for populating the p levels of inert gas atoms. It is assumed that the most likely channel for d-level population is direct excitation of atoms by secondary electrons and excitation transfer from buffer gas atoms, with p levels being populated by transitions from upper levels. Dissociative recombination of mercury molecular ions with electrons is the basic process responsible for populating the 73S1 level of mercury atoms.
