Electron Scattering in Atomic and Molecular Hydrogen

An apparatus for generating an electron beam of known energy was designed to rotate about an axis perpendicular to the beam, and through which it passed. Those electrons scattered in the neighborhood of the axis through a given angle entered an analyzer in which an energy spectrum was obtained. The scattering gas was hydrogen admitted from the center of a discharge tube. When the discharge was in operation it was estimated that more than 60 percent of the hydrogen was in the atomic condition. At a given electron velocity and angular setting the electron energy spectrum could be analyzed into component peaks which were interpreted as due to elastic, inelastic and ionizing collisions. One inelastic loss of about 8 volts was found to occur and several were observed in the neighborhood of 12.5 volts. From the areas under these peaks the number of electrons scattered through the particular angle could be computed. From these results the number of electrons scattered elastically was plotted as a function of the angle both for the case of atomic and molecular hydrogen. The scattering in both cases was very similar. In the former case the results agreed well within the experimental error with the theoretical curves predicted by quantum mechanics.