Assessing the Accuracy of Mass Attenuation Coefficients for Soft X-ray EPMA.

The use of soft X-rays in electron probe microanalysis (EPMA) has gained renewed interest over the past decades due to the advent of new detector technologies. Because X-ray absorption is the dominant correction for soft X-rays, a reliable set of mass attenuation coefficients (MACs) is needed for accurate composition determination. Although several MAC tabulations cover the soft X-ray range, the accuracy of such tabulations below 1 keV is not firmly established. In this study, we assess the accuracy of MAC tabulations in the soft X-ray region by comparing tabulated values for Be, B, C, N, O, and F Kα X-rays with experimental data available in the literature. We find that the 1993 semi-empirical MAC compilation of Henke et al. [(1993). Low-energy X-ray interaction coefficients: Photoabsorption, scattering, transmission and reflection at E=50-30000 eV, Z=1-92. Atom Data Nucl Data Tables54, 181-342] and the more recent theoretical MAC calculations of Sabbatucci and Salvat [(2016). Theory and calculation of the atomic photoeffect. Rad Phys Chem121, 122-140] perform slightly better than the rest of the considered tabulations. The Sabbatucci-Salvat dataset also provides the best agreement with the few existing experimental measurements for Al L2,3M X-rays.