The Velocity and Number of the Photo-Electrons Ejected by X-Rays as a Function of The Angle of Emission

Magnetic spectra of the electrons ejected by x-rays from thin metallic films at angles ranging from 0° to 180° with the direction of the x-ray beam have been obtained by the method of Robinson, de Broglie, and Whiddington. To the degree of accuracy of the measurements (one-half of one percent) the maximum velocity of ejection is exactly the same in all directions. With thin foils of the heavier elements the number of electrons leaving the foil with this maximum velocity in the various directions (determined by the intensity of the edges) is approximately the same. With radiators of small density, or with sputtered films so thin that Wentzel's criterion for "single" scattering holds, the number of electrons leaving the foil is greatest in a direction a little forward of perpendicular to the direction of the x-ray beam. Rutherford's theory of nuclear scattering applied to electrons gives an explanation of these results if the assumption is made that all the electrons start out from the atom in the same direction.