Resonance Scattering and the Drift Motion of Electrons through Gases. II

In a previous paper, recent observations of pressure-dependent electron drift velocities in gases were interpreted in terms of new ${\mathrm{H}}_2^{-}$ or ${\mathrm{N}}_2^{-}$ temporary ion states. In this paper, it is pointed out that both the lifetime $\tau$ of the ion state and the mean electron-molecule collision frequency for trapping collisions can be obtained from experiment. The existing data are shown to yield an upper limit of $\tau \le {4.10}^{-9\mathrm{}}$ sec for hydrogen. It is thought that much shorter lifetimes can actually be measured, and clues to this end are given.