Luis Velasquez-Garcia (Heller)
imilar to electron field emission, field ionization of gas molecules is produced by quantum tunneling of electrons through a potential barrier that is narrowed by the presence of a local high field. However, field ionization is a quite different physical phenomenon. In field ionization, the electron flux goes from the neutral gas molecule to the field enhancer. Also, the height of the potential barrier is defined not only by the workfunction f of the field enhancer surface but also by the ionization potential I of the gas molecule. Field ionization requires substantially higher fields, typically of the order of 108 V/cm. Field ionization has two distinctive regimes of operation.