The spacial distribution of photoelectrons produced by X-rays

Abstract

Investigations on the initial directions of emission of photoelectrons produced by X-rays show that the distribution depends on the direction of propagation of the rays, whilst in the case of a polarised beam it depends also on the direction of the electric vector of the incident radiation. The distribution of the initial directions of the photoelectrons relative to the direction of the incident X-ray beam is usually called the “longitudinal distribution,” whilst that relative to the plane containing the electric vector and the rays, in the case of a polarised beam, is termed the “lateral distribution.” The present paper will deal only with the longitudinal distribution of the photoelectrons. In the first place a survey of the experimental situation will be given, from which it will be seen that the results of previous observers are not in a satisfactory state of agreement. Secondly, it is the purpose of this paper to give an account of the authors’ own experiments on the longitudinal distribution in which it is hoped that some of the possible errors giving rise to the discordant results of previous investigators have been eliminated. The main interest of the present work lies in the results obtained for the asymmetry, which show that the average forward momentum of a photoelectron is nearly 40 per cent, greater than that of an absorbed quantum. This result of our experiments was first announced in a thesis published in April, 1927.