L X-ray production cross-section ratios for protons incident on high-Z atoms: A test of ECPSSR theory and newly recommended vacancy de-excitation parameters

The X-ray intensity ratios Lβ/Lα and Lγ/Lα for six heavy elements have been measured using a Si(Li) detector coupled to both analog and digital signal processors. The proton energies were chosen to ensure that possible united atom (UA) and intra-shell (IS) effects would be small, thereby ensuring that the experiments were a direct test of the ECPSSR together with the L subshell fluorescence and Coster–Kronig probabilities. Careful attention was paid to reducing recognized uncertainties in the fitting of the spectra, with the desired intensity ratios being extracted from a procedure that assumed the DF radiative transition rates of Scofield to be correct. Experiment and ECPSSR theory agree closely when the fluorescence and CK probabilities from a recent critical review are adopted in preference to those commonly used in earlier work. This result provides a significant improvement in the database used for PIXE analysis, and it paves the way for more definitive studies at lower proton energies, aimed at testing predicted UA and IS corrections.