Decrease ofF-Center Photoconductivity Upon Bleaching

A quantitative study of the rapid decrease in photoconductivity accompanying the relatively less rapid bleaching of $F$ centers in additively colored KCl is reported. The experimental observations agree, except during very early stages of bleaching, with an equation for the variation of sensitivity with total light absorbed derived upon the assumption that negative-ion vacancies are created and traps of smaller cross section are filled during bleaching. Except during early stages, where several kinds of traps may be present in low concentration, only one kind of trap other than the negative-ion vacancy need be considered.