Direction of Photo-Electron Emission

Direction of emission of photoelectrons from hydrogen, air and argon irradiated by Mo $\mathrm{K}\alpha$ x-rays.—Photographs of the photo-electron tracks in a Wilson expansion chamber through which a narrow beam of monochromatic Mo $\mathrm{K}\alpha$ x-rays were passed were taken with a stereoscopic camera. The direction of the paths with respect to the x-ray beam was determined from measurements made with a specially designed stereoscopic comparator. 445 tracks were studied of which 231 were in argon, 123 in air and 91 in hydrogen. Curves showing the frequency of occurrence of different angles of ejection have a fairly sharp maximum for angles of about 70° with the forward direction of the x-ray beam. The curves are similar for the three gases studied except that the maximum in the case of hydrogen is somewhat sharper than for the other two gases.