Electron-loss cross sections for fast, metastable and ground-state helium atoms in gases and metal vapours

Abstract

Electron-loss cross sections for metastable He(23S) atoms have been measured in H2, He, N2, Ne and Ar at energies between 450 and 1300 keV and in Li and Na vapours at energies between 100 and 1300 keV. Electron-loss cross sections for 50-4000 keV ground-state He(11S) atoms in Ne, Li and Na are also presented. Metastable-atom populations of neutral helium beams formed by the neutralisation of He+ ions in He or N2 have been measured at beam energies of 300 keV in He and 300 keV and 1 MeV in N2. The measured electron-loss cross sections for metastable and ground-state helium atoms colliding with noble-gas atoms are, at high energies, in good agreement with recent theoretical estimates in the free-collision model.