The Angular Distribution of Electrons Scattered Elastically and Inelastically in Mercury Vapor

Abstract

A long electron gun was mounted to rotate about a well-shielded scattering region from which electrons scattered by gas molecules through a definite angle from a beam of small cross-section were collected, and their velocities determined, by a stationary collector containing an efficient Faraday cage, 6.0 cm in length. Angular distribution curves for electrons scattered elastically, for electrons scattered due to excitation of the atom (mainly 6.7 volt energy loss), and for electrons resulting from ionizing impacts are presented for 80, 120, 230, 490, and 700-volt electrons. In general, for a particular group, the curves are steeper the higher the velocity of the incident electron. The elastic group shows a diffraction pattern at large angles and the positions of the peaks agree well with those found by Arnot. The curves for the excitation group are much steeper than are those for the elastic group, and fall to very small values at large angles. The curves for the ionization group are also steeper but not so steep as the excitation group; at large angles the scattering is due mainly to slow electrons of this group. The ionization group is divided into sections and further characteristics are observed. Numerical integration of these curves gives the cross-sectional area for collision, the efficiency of ionization, and the efficiency of excitation.