This letter reports an investigation of the vacuum ultraviolet emission from gaseous xenon excited with a 4-nsec 10-kA cm-2 electron beam. The observed decrease in the emission lifetime at 171.5 nm for high xenon number density is due to a quenching process intrinsic to xenon. Treatment of the quenching data yields a radiative lifetime of 130 ± 20 nsec for the excited xenon diatomic, and a quenching constant of 5.1 × 10-13 cm3 atom-1 sec-1. Thus, the theoretical threshold for laser action in excited diatomic xenon molecules is ∼ 26 times higher than had been previously anticipated from the 5-nsec lifetime observed in liquid xenon. © 1973 American Institute of Physics.