Electron impact ionization by drifting electrons in weakly ionized plasmas

The expression for electron impact ionization rate by a Maxwellian electron population drifting with respect to a uniform neutral atom background is derived. Depending on electron temperature, drift speeds between one to five times electron thermal velocity produce increments in the ionization rate from two to seven orders of magnitude. Local ionization takes place over shorter distances than predicted for nondrifting electron populations and the results agree with previous experimental evidence on ionizing plasma double layers and electron attracting sheaths.