The effective cross‐section of trapping, σeff, and the “frequency” factor ωeff measured in experiments in the case of attractively charged localization centres may strongly differ from the real gaskinetical σk and ω, but for the ratio yields ωeff/σeff = ω/σk. The greater the difference the less is the carriers mean free path l. In this sense, for example, the alkali halides are of great interest. The free carriers distribution function with respect to the localization centres documentclass{article}pagestyle{empty}begin{document}$ overleftarrow {eta (r)} $end{document} and documentclass{article}pagestyle{empty}begin{document}$ overrightarrow {eta (r)} $end{document} in the cases of trapping and release processes, respectively, complete each other to the thermal equilibrium function ηT(r). Copyright © 1968 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim
