The ratio of the capture cross section of a sensitizing center for a photoexcited hole to the subsequent capture cross section for a free electron, inn‐type photoconductors, can be determined from the measurement of the thermal quenching of photoconductivity as a function of excitation intensity. The magnitude of the ratio gives information about the charged state of the sensitizing center. A summary of many such measurements on seven different photoconductors of type II–VI or III–V supports the hypothesis that doubly charged sensitizing centers are present in some of these materials, but that singly charged sensitizing centers are present in the majority.