(e,2e) ionization studies of the stable noble gases in a coplanar symmetric geometry

Abstract

A comprehensive set of coplanar symmetric ($e$,2$e$) ionization data are presented for the stable noble gas targets helium, neon, argon, krypton, and xenon. The incident electron energy ranged from 1.2 to 200 eV above the ionization potential of the target atoms, so as to span from near threshold to the high-energy regime. Data are presented with high precision, and cover a wide angular range from forward scattering where the electrons were detected at angles from 30\ifmmode^\circ\else\textdegree\fi{} to the incident electron beam, through to the backscatter region where the deflection angle was up to 130\ifmmode^\circ\else\textdegree\fi{}. The data are normalized to unity at each energy, and are compared to previously published theoretical calculations where available. The data show complex changes in the structure of the measured cross sections, depending upon both the energy and selected target. Similarities and differences in the cross sections were found between the different targets, which provide a challenge to future models of the ionization process.