Low-velocity effects in L-subshell ionisation of Ta and W induced by proton, deuteron and alpha impact

Abstract

L-subshell X-ray production cross sections were measured for Ta and W bombarded by 0.20 to 0.90 MeV u-1 protons and deuterons and by 0.2 to 0.45 MeV u-1 alpha particles. Lalpha Lgamma 1 and Lgamma 2,3 lines were selected to convert X-ray production cross sections into ionisation cross sections. The deuteron to proton-induced cross section ratios show that the Coulomb and energy loss effects are well accounted for in all subshells. The alpha to deuteron-induced cross section ratios show that the theory overcorrects the binding effect, the theoretical ratios being lower than the experimental ones by roughly 25% for the L3 subshell and 75% for the L2 subshell. It is argued that this difference between the ratios, and the poor agreement on the L2-subshell absolute cross sections, may be accounted for by assuming a 10-20% deviation in the values used for the fluorescence and Coster-Kronig yields and for the emission rates; such a deviation may be induced by the projectile.