The Direction of Ejection of Photo-electrons Produced by X-rays

Stereoscopic photographs of photo-electrons produced by 40 kv Mo $\mathrm{K}\alpha$ x-rays, were examined by a stereoscopic comparator which gave a quantitative measure of the initial direction of ejection in space. The measurement of twenty-four distinct tracks in a series of twenty-nine pairs of photographs showed that the most probable angle of ejection was about 70° with the primary beam. This supports the view that the electric vector of the radiation plays a very important part in the production of photo-electrons. The small forward or backward component, noticed in many tracks, must come from the random momentum of the electron in its orbit before ejection.