Scattering of Low-Energy Electrons by Atomic Hydrogen

Abstract

The total cross section for the scattering of electrons by atomic hydrogen has been measured as a function of electron energy from 3.1 to 12.3 ev. The basic measurement compared the number of electrons scattered from a region defined by the intersection of an electron beam and a chopped molecular beam with the number scattered when the hydrogen beam was partially dissociated. By measuring the degree of dissociation with a mass spectrometer, one may obtain the ratio of cross sections of atomic and molecular hydrogen for a given energy. The absolute atomic values were calculated from these ratios and molecular hydrogen values obtained from the literature. In the experiment most of the scattered electrons were detected (the angular resolution was about 25°), thereby differing from a previous measurement by Brackmann, Fite, and Neynaber. Our results are in good agreement with several theoretical estimates, e.g., that of McEachran and Fraser.