Electron-impact dissociation of HeH⁺: absolute cross sections for the production of He^q+(<i>q</i>= 1–2) fragments

Absolute cross sections have been measured for electron-impact dissociative excitation and ionization of the helium-hydride ion (HeH+) leading to the formation of helium ions Heq+ (q = 1–2). Measurements have been performed for electron energies ranging from the respective thresholds up to 2.5 keV. For He+ production, the maximum absolute cross section for dissociative excitation is found to be (2.5 ± 0.2) ×10−17 cm2 (around 40 eV), while for dissociative ionization, it is found to be (2.1 ± 0.1) ×10−17 cm2 (around 135 eV). For He2+ production, only the inclusive absolute cross section is presented, without attempting to isolate any distinct contribution, and it is measured to be (2.6 ± 0.2) ×10−19 cm2 (around the maximum, 195 eV). Appearance energies for He+ and He2+ are determined to be (11.2 ± 0.5) eV and (66.5 ± 1.0) eV, respectively. Kinetic energy release and angular distributions are obtained, at specific incident electron energies.