Distorted-wave ionization and x-ray production cross sections of the K shell of Cu and the L shells of Ag, In, and Sn by positron impact

We study the ionization cross sections of the K shell of Cu and the L shells of Ag, In, and Sn by positron impact using the distorted-wave Born approximation, focusing on the near-threshold energy range (below 40 keV) to compare with recent measurements. The distorted-wave formalism proves to be an appropriate approach, especially to describe the shape of the cross-section curves for positrons accurately. Furthermore, we calculate x-ray production cross sections of the considered L shells having recourse to two sets of atomic relaxation parameters involved in the conversion from ionization to x-ray production cross sections. The 5%–10% differences in the theoretical values calculated with these parameter sets are apparently not large enough to explain the discrepancy between the distorted-wave curves and the experimental data, particularly for Ag. Other sources of uncertainty that could be affecting these comparisons are discussed.