Chemisorption effects on polarization of radiation from inelastic ion-surface scattering

Ar+ ions were excited by scattering from an aluminium reference surface at near grazing incidence under uhv conditions. The relative circular polarization Stokes parameter S/I of the decay radiation from the 4p'2Fsub(7/2) level at 461 nm was measured, giving S/I=30-40% in the 60-80 keV energy range. These results are comparable to those for a stainless steel reference surface, for which polarization changes due to chemisorption were observed. Measurements do not show a significant change in the polarization fraction when N2 and H2 gases are chemisorbed on the aluminium surface, but O2 gas produces a large increase in the transition intensity, and a significant reduction in S/I. The orientation of this level may be the result of multiple collisions followed by electron transfer. (orig.)