Collision spectroscopy with aligned and oriented atoms. II. Charge exchange in He+-Na(3p) collisions

Abstract
Electron capture processes in the He+-Na(3p) collision are experimentally investigated in the 0.5-3 keV energy range using time of flight spectroscopy. The excited target is produced with a defined alignment or orientation by laser pumping. The sigma 3p/ sigma 3s ratio of total cross sections for charge exchange in the He+-Na(3p) and He+-Na(3s) collisions is measured and enables a first evaluation of the sigma 3p cross section which amounts to 70 AA2 at keV energies. The He*(n=2) and He*(n=3) channels are populated: the He*(n=2) reaction is dominant at low energies whereas the He*(n=3) reaction becomes important at higher energies and/or scattering angles.