Electron loss from fast metastable and ground state helium atoms in passage through gaseous targets

Abstract

A beam attenuation technique developed previously in this laboratory has been used to obtain cross sections sigma 01 and sigma 0*1 for fast ground state and metastable helium atoms in helium, neon, argon, krypton and nitrogen at impact energies within the range 60-350 keV. Values have also been obtained for targets of hydrogen and helium in the range 10-40 keV. Measured cross sections sigma 0*1 are shown to be in good agreement with values calculated recently by Bates et al. for targets of H2, Ne, Ar and Kr using a classical impulse approximation. The observed energy dependence of sigma 01 in the case of targets of hydrogen and helium is also found to be in good agreement with that predicted by the recent calculations of Bell et al. based on the first Born approximation.