The transfer of charge following absorption of a light pulse by colored KCl at room temperature in an electric field was studied as a function of the field. At sufficiently high fields the charge should reach a saturation value from which the quantum yield for photoionization eegr; can be obtained directly. Saturation is difficult to achieve experimentally in KCl; however, in 2 of 12 samples studied, saturation was clearly established and eegr; was found to be 0.49plusmn;0.07 and 0.17plusmn;0.03. Taking eegr; to lie between about 0.2 and 0.5, the trapping cross section for negative ion vacancies lies between 50percnt; and 80percnt; of the capture cross section at room temperature.
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