The status of theoretical L-subshell ionization cross sections for protons

Abstract

Accuracy of PIXE analyses depends on inner-shell ionization cross sections. These cross sections are often calculated in the ECPSSR theory; results of its variant (that uses DHS wavefunctions) are employed in the gupix package. While the ECPSSR theory agrees well with massive compilations of K x-ray production, it deviates systematically from L-subshell data – in particular, L 1 and L 2 cross sections. Various modifications of the ECPSSR theory and their results are reviewed versus the empirical database from Orlic for 0.3–3.5 MeV protons on 45⩽ Z 2⩽92 targets. Comparison with this database does not give a clear choice between the ECPSSR and the ECPSSR with all modifications. Independently of the chosen theory and because of the increasing scatter in the data with the decreasing proton energy, PIXE packages that may rely on reference cross sections for L 1 x-ray production in lanthanides by 0.2-MeV protons could err by an order of magnitude in the determination of the concentration of these elements.