The stopping of slow75As recoil atoms in He, Ne and H2

Abstract

The slowing down of75As recoil atoms with energies ≲10eV in He, Ne and H2 was investigated by measuring Doppler-widened line profiles of the 265 keV gamma line emitted by the recoil nuclei. The line profiles contain information on the stopping powers of gases for heavy ions with initial velocities υ≲3·105 cms−1. They are analyzed in terms of the continuous slowing down theory developed by Falcone et al. The profiles observed with He and Ne are well described by assuming the stopping power to be based on Lenz-Jensen elastic interaction between recoil and moderator atoms. The profiles observed with H2 do not agree with predictions based on that interaction. The stopping power of H2 for the75As recoil atoms is found to be larger than that of He.