Selection of Monochromator Crystal for Pb L‐, Br K‐, and Ag K‐Edge <scp>XANES</scp> Using a Laboratory‐Based Spectrometer

ABSTRACT We recorded Pb L3‐, Br and Ag K‐edge XANES spectra using conventional laboratory‐based spectrometer using various monochromator crystals: Si(400), Si(620), Si(800), Si(12 4 0), Ge(840) and Ge(880). Undesirable low‐index reflections from the single crystal monochromator and the characteristic X‐ray lines were suppressed using appropriate thick aluminum filter, and the corresponding optical setting were discussed. The absorption edge of various Pb compounds at Pb L3‐edge was evaluated using two methods: E 0 ‐half, defined as the position at the half‐height of normalized XANES, and E 0 ‐diff, defined as the peak position of the first derivative of XANES. The influence of energy resolution on the apparent absorption edge and the resulting chemical shift were discussed. The use of a monochromator crystal with small d‐spacing resulted in XANES spectra of higher resolution, comparable to those recorded at synchrotron radiation facilities. The energy resolution did not affect the apparent chemical shift derived from E 0 ‐half, but significantly affect the shift evaluated from E 0 ‐diff. The first derivative of Pb L3‐edge XANES spectra with lower energy resolution is suggested to be preferable for oxidation state analysis of unknown samples. The application of high‐order reflections Ge(880) at Ag K‐edge lab‐XAFS provided XANES spectra, which are applicable for chemical state analysis.