Stepwise ionization in a glow discharge cathode layer in argon

A contradiction between the classical theory of the glow-discharge cathode layer applied for an argon plasma and the cathode-drop potentials measured for different cathode materials is shown. This contradiction can be eliminated on the assumption that the ionization equilibrium in the cathode layer is stepwise. A theory of a glow-discharge cathode layer for a stepwise mechanism of atomic ionization by electron impact and a criterion for its implementation are presented. The stepwise ionization mechanism in the cathode layer also leads to a more efficient way of the formation of secondary electrons on the cathode (in comparison with the classical case) due to quenching of excited atoms.