Polynomial approximation to universal M-shell ionisation cross-sections induced by H+ and He2+ ions

The calculation of ionisation cross-sections induced by H+ and He2+ ions in efficient ways for inclusion in simulation programmes to determine the X-ray intensities is still extremely useful, in spite of the significant computer power available nowadays. Particle-induced X-ray emission studies have been mostly carried out using K-shell and L-shell X-ray emission. However, the new microcalorimeter detection systems available will make M-shell and higher shell X-ray emission data increasingly important. Quantification and simulation of X-ray intensities require one to be able to compute the ionisation cross-sections, which can be carried out using the ECPSSR theory. Nevertheless, this is not an efficient process, and therefore, in previous work, K and L-shells universal ionisation cross-section curves were found as well as polynomial approximations to the universal curves. In this work, polynomial approximations to the M-shell universal ionisation cross-sections are presented, and calculated ionisation and X-ray production cross-sections based on the polynomial approximations are compared with results from literature. These polynomial approximations were included in the X-ray intensities simulation programme DT2simul, based on LibCPIXE, and the results obtained are compared with experimental data for several elements and compound samples. Copyright (c) 2013 John Wiley & Sons, Ltd.