Accurate elemental quantification of materials by X-ray detection techniques in electron microscopes or microprobes can only be carried out if the appropriate mass absorption coefficients (MACs) are known. With continuous advancements in experimental techniques, databases of MACs must be expanded in order to account for new detection limits. Soft X-ray emission spectroscopy (SXES) is a characterization technique that can detect emitted X-rays whose energies are in the range of 10 eV to 2 keV by using a varied-line-spaced grating. Transitions producing soft X-rays can be detected and accurate MACs are required for use in quantification. This work uses Monte Carlo modeling coupled with multivoltage SXES measurements in an electron probe micro-analyzer (EPMA) to compute MACs for the L2,3-M and Li Kα transitions in a variety of aluminum alloys. Electron depth distribution curves obtained by the software MC X-ray are used in a parametrized fitting equation. The MACs are calculated using a least-squares regression analysis. It is shown that X-ray distribution cross-sections at such low energies need to take into account additional contributions, such as Coster–Kronig transitions, Auger yields, and wave function effects in order to be accurate.

Quantification of first series transition metal Lα X-rays is hampered by absorption and in some cases transition probabilities (fluorescence yields) varying with chemical bonding. Compound mass absorption coefficients for Fe Lα were measured in the olivine solid solution series [Forsterite (Mg2SiO4) to Fayalite (Fe2SiO4)] and the mass absorption coefficients for Fe Lα absorbed by Fe were calculated. The mass absorption coefficients vary systematically between Fo83 and Fo0. Using the measured mass absorption coefficients for both standard and unknown and by correcting for a systematic discrepancy, consistent with varying partial fluorescence yields, a good agreement between calculated k-ratios and measured k-ratios is achieved. The systematic variations allow quantification of unknown k-ratios. The described method of quantification requires modification of matrix correction routines to allow standards and unknowns to have different mass absorption coefficients, and to incorporate solid solution mass absorption coefficients and partial fluorescence yield corrections derived from regression of experimental data.

Publicly available mass absorption coefficients (MAC) tables do not comprise accuracy data and are typically created from relatively old sources. The idea of comparing tables is not new (De Boer), but current software tools make it possible to quickly develop interactive software to analyze the discrepancies in finer detail and get hints to the reason for the difference. Such a tool has been created and used to compare six public domain databases. Several reasons for sizeable discrepancies have been identified, ranging from probable typos to misplaced or missing absorption edges. In addition to the discrepancies that can reasonably be pigeonholed huge differences exist for all elements below 1000 eV. Since there are many cases where reliable standards are scarce or inexistent the development of a better, consistent MAC table especially in the low energy and low Z regions, and with reliable error bars is a requirement for further development of XRF methods in many advanced fields such as waste management, user safety (RoHS), renewable energy sources, and many more. The international initiative for improved FP which involves several industrial and academic organizations aims to address the issue as a whole, i.e. not only for MAC. Creating such a complete database requires considerable resources; the comparison tool may alleviate the effort in the MAC field by readily showing which energy regions and elements deserve more attention.