Delta -electron spectroscopy of multiply ionising proton-rate-gas collisions

Abstract

Doubly differential cross sections for delta -electron ejection in proton-rare-gas collisions have been studied at ejection angles of 50, 90 and 120 degrees , electron energies of about 10 to 550 eV, and incident energies around 300 keV. Performing a charge-state analysis of the recoil ion in coincidence with the delta electrons we were able to distinguish between single and multiply ionising collisions. It was observed that the relative importance of multiple ionisation events is smaller at forward compared with backward ejection angles and increases with increasing energy of the delta electron. An analysis in terms of an ionisation model of independent electrons gives fair agreement with the experimental data.