Electron-impact-ionization cross sections ofH2for low outgoing electron energies from1to10eV

Abstract

Theoretical and experimental fully differential cross sections are presented for electron-impact ionization of molecular hydrogen in a plane perpendicular to the incident beam direction. The experimental data exhibit a maximum for $1$-eV electrons detected ${180}^{\ifmmode^\circ\else\textdegree\fi{}}$ apart and a minimum for $10$-eV electrons. We investigate the different physical effects which cause back-to-back scattering and demonstrate that, over the energy range from $10$ to $1$ eV, a direct transition is observed from a region where Wannier threshold physics is essentially unimportant to where it completely dominates.