The theory of volume effect in photoelectric emission is developed. Formulae are derived for the rate of electron excitation and for the photoelectric yield. The calculated threshold frequencies for volume effect are 5.91×${10}^{14}$ and 5.69×${10}^{14}$ for sodium and potassium respectively. The estimated photoelectric yields for these metals are of the same order of magnitude as those calculated for surface effect and are comparable with those observed experimentally. The volume effect should not, therefore, be neglected except in the immediate neighborhood of the threshold frequency. Approxmate estimation indicates that light absorption of sodium and potassium in the visible and ultraviolet regions should be largely due to quantum excitation of electrons. Accurate calculation of electron excitation and absorption requires detailed knowledge of electron wave functions.

• Received 18 May 1945

DOI:https://doi.org/10.1103/PhysRev.68.43