Dissociative ionization by electron impact. I. Protons from H2

Abstract

A new apparatus designed to investigate various aspects of the electron impact dissociative ionization process is described in detail. It is shown that the angular distributions obtained for protons from the ² Sigma _u⁺ state of H₂⁺ are consistent with theoretical arguments and confirm the results of previous measurements. The first angular distribution of protons from the ² Sigma _g⁺ state of H₂⁺ is also reported. Absolute cross sections for the production of protons from both the ² Sigma _g⁺ and ² Sigma _u⁺ state of H₂⁺ at electron energies close to the respective thresholds are also presented. The ratio H⁺/H₂⁺ is measured as a function of incident electron energy for ions originating from the ² Sigma _g⁺ state.