The near infrared laser emission from Xe in Ar and He mixtures has been investigated experimentally in an ionizer‐sustainer mode, and theoretically. An efficiency of 1.3% has been achieved from Ar : Xe, 150 : 1, at 1900 Torr with aproximately 75% of the output contained in a single line at 1.73 μm. Based on a detailed kinetic study of the discharge, the laser behavior is attributed to a two‐stage excitation in which a large excited‐state population is created during the first portion of the discharge followed by excitation and ionization of these excited states and strong lasing during the remaining low‐field portion. The processes leading to the strong emission include electron‐impact excitation from low‐lying excited states, dissociative recombination pumping, and cascade pumping from higher‐lying levels, all of which means that the original excitation energy is being recirculated. The desired high Ar pressure is explained on the basis of providing an impedance match to the sustainer circuit and because the elastic (momentum) losses, at low fields, are nominal allowing a small excited‐state density to dominate the fractional‐loss spectra.