The Surface Heat of Charging

Abstract

In recent papers by Bridgman, Langmuir and Tonks, and the author, the deviation of the constant $A$ of thermionic emission from the theoretical value has been linked with the surface heat of charging and the temperature variation of the photoelectric threshold. In the present paper, at least a part of this effect is explained by the heat expansion of the material together with the dependency of the work function on the volume. Numerical calculations both for the deviations of $A$ and for the temperature change of the threshold are made and compared with experiments. Before deciding whether the explanation given here is complete it will be necessary to calculate the space-charge effect of the electrons in the transition layer on the surface of the metal.