State-selective electron capture by slow S3+ recoil ions in H, H2 and He

Abstract

Translational energy spectroscopy has been used to study electron capture by slow S3+ ions from a recoil ion sources. These ions are important in astrophysical plasmas. Cross sections for state-selective electron capture by S3+ ions in H, H2 and He have been determined at energies within the range 2.4-9.0 keV. The main excited product channels have been identified and their relative importance has been assessed. In the case of H and He a multichannel Landau-Zener model has been used to predict cross sections which have been compared with experiment. The presence of S3+(4P) metastable as well as S3+(2P degrees ) ground-state ions in the primary beam has been clearly demonstrated. Electron capture by ground-state ions is dominated by 3p electron capture. For H and H2 the majority of channels also involve 3s to 3p excitation of the projectile core.