Ion-assisted electron emission from a cathode in an electric arc

The effect of the presence of ions near the metal surface on the electron field emission by an arc cathode is studied theoretically. An important electron emission process is shown to be mediated by the neutralization of the ions: one electron from the metal is captured by each ion to form an excited neutral atom which is then ionized by the macroscopic field. The neutralization - ionization rates are obtained for ions in front of a metal surface for different fields and then used to evaluate the electron emission. This ion-assisted process contributes significantly to the electron emission, well below the top of the Schottky barrier. The contribution of this resonant process to the cathode heating is also evaluated.