Harmonic X-ray Incident Energy Calibration for X-ray Spectroscopy at the K-Edges of Phosphorus, Sulfur, and Chlorine.

The tender X-ray regime in X-ray absorption spectroscopy (XAS) uses incident X-ray energies between the so-called soft and hard X-ray regimes, approximately between 2 and 4 keV, which includes the K-edges of phosphorus, sulfur, and chlorine. Applications of tender XAS are rapidly increasing, with recent studies including contributions from geochemistry, catalysis, chemistry, and environmental and life sciences. Despite this increased activity, there is no clear consensus about incident energy calibration at the phosphorus, sulfur, and chlorine K-edges, potentially causing confusion when the results of different research groups are compared. Here, we attempt to resolve the confusion by using the Si(333) harmonic of a Si(111) double crystal monochromator in combination with well-characterized first transition element foils to evaluate the corrected calibration energies for some relevant standard compounds.