The Impact of Chemical Bonding on Mass Absorption Coefficients of Soft X-rays

Abstract

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.

High-accuracy experimental determination of photon mass attenuation coefficients of transition metals and lithium fluoride in the ultra-soft energy range

“…Experimental high-precision data comes from LNHB. 21 The data were fitted using Origin 2020 14 defining the non-linear fitting function eqn 2 using the Levenberg–Marquardt Least-Squares Algorithm. The data for μ / ρ ox comes from tabulated ultra-high precision experimental measurements.…”

“…Addressing discrepancies in tabulated fundamental parameters of lithium, potentially stemming from non-valid calculation models, is imperative. 14 In practical applications, lithium is frequently found in samples alongside transition metals (e.g., batteries) or in metal alloys containing aluminum. Therefore, the aim of this work is to experimentally study the MACs of lithium fluoride, aluminium and transition metals with atomic numbers from 24 to 29 in an energy range from several hundreds of eV down to 40 eV as they all present absorption edges in this range.…”

“…Addressing discrepancies in tabulated fundamental parameters of lithium, potentially stemming from non-valid calculation models, is imperative. 14 In practical applications, lithium is frequently found in samples alongside transition metals ( e.g. , batteries) or in metal alloys containing aluminum.…”

Electron Probe Microanalysis of Transition Metals using L lines: The Effect of Self-absorption

“…for a range of incident electron energies E 0 i , where i goes from 1 to the number of incident electron energies N. Equation ( 27) resembles that used by Pouchou & Pichoir (1988) to determine experimentally mass absorption coefficients using the electron microprobe (see also Kyser, 1972;Mackenzie, 1991;Pöml & Llovet, 2020;Rudinsky et al, 2020), where the theoretical X-ray intensity I h would be replaced by a measured X-ray intensity and a multiplicative factor would be added in equation ( 27) so as to allow measuring X-ray intensities in relative units (Pöml & Llovet, 2020). Obviously, the accuracy of the mass absorption coefficients obtained in this way will depend on the accuracy of the theoretical models used to calculate the different factors in equation ( 26).…”