The CasaXPS/Kratos R.S.F. value (of 0.6) for the Mg KLL Auger line tends to significantly overestimate the amount of magnesium present compared to the quantitative values found from the Mg 2p and Mg 2s lines. A new R.S.F. value calculated from standard samples (magnesium metal and magnesium oxide) has been developed for use on samples where the Mg 2p or Mg 2s peaks are either too small or overlapped with other species. A value of 4.3 +/- 0.3 was found to work quite well. Use a background encompassing the main peak of the Mg KLL line extending from approximately 315 eV to 298-300 eV. Interference from strong C 1s loss structure can be mitigated by shifting the lower binding energy background endpoint to a slightly higher binding energy.
Mg KLL Auger R.S.F. = 4.3 +/- 0.3
Magnesium reference spectra used for this calculation and showing the full Mg Auger peak-set are presented in the link.