Slow Electron Scattering and the Apparent Electron Affinity of Mercury

Abstract

The scattering of slow electrons by gaseous molecules is discussed with the object of explaining the curves obtained when the apparent scattering area is plotted against a function of the electron velocity. The peaks frequently observed at about the ionization potential for most substances and the abnormally high values for the alkali metals are explained as being due to the formation or presence of positive ions. The rise in the curves for some substances, as the accelerating potential is diminished below the ionization potential, is explained as the result of an attractive force between the electron and the neutral molecule. It is shown that this attractive force for mercury approximates an inverse fourth-power law. From this law and an assumption of the diameter of the negative mercury ion, a reasonable value for the apparent electron affinity of mercury is calculated.