A possible explanation of the selective photoelectric effect

Introduction.—The known facts about the normal and the selective photoelectric effect have recently been assembled and discussed by Campbell. The theoretical speculations of this paper are the outcome of discussions with him. I take this opportunity of acknowledging my indebtedness to him, for without these discussions I could never have attempted to formulate any such theory. In the normal photoelectric effect the number of electrons emitted per quantum absorbed increases regularly as the frequency of the light is increased beyond the threshold. (We are throughout this paper only concerned with frequencies of the order of the threshold frequency, usually less than twice as great and never several times greater.) In certain cases, however, when the electric vector of the exciting light lies in the place of incidence, the number of emitted electrons shows a strong fairly narrow maximum superposed on the normal increase, when plotted against the frequency. This is the selective effect. The superposed maximum may be quite near the threshold.