Evidence for the Formation of Neutral Rare-Gas Molecules by Electron-Beam Pulses

Intense emission and absorption signals in the visible and near-infrared regions have been induced by submitting Ne, Ar, Kr, and Xe and binary mixtures of these gases to brief intense pulses of 500-keV electrons. Measurements of the intensities of these signals as functions of time have been made with a time resolution of ∼ 40 nsec. The majority of the observed signals are attributed to 1s–2p atomic transitions. The lifetimes of the 2p atoms are shown to have been of the order 10−7–10−6 sec and to decrease with increasing pressure at 200–1500 torr. Absorption signals appearing in the near-infrared region unaccompanied by characteristic atomic emission signals were strongly inhibited by presence of a heavier rare gas and exhibited longer rise times than the atomic signals. These near-infrared absorption signals are tentatively attributed to neutral, probably diatomic, rare-gas molecules.