APPARENT DISCREPANCY BETWEEN MEASURED AND TABULATED M ABSORPTION EDGE ENERGIES

摘要

We report gold photocurrent and reflectivity measurements made at the Daresbury Synchrotron Radiation Source. We find that the measured M-edge energies differ from tabulated values by about 30 eV for the M_(IV) and M_V edges. The effect is also apparent in Pt and Pb and in literature reports for Ir. We attribute the discrepancy to the use of limiting absorptions based on X-ray photoelectron spectroscopy (XPS) values. For the M_(IV) and M_V edges, the differences are accentuated by the very slow onset of the 3d → f transition. An analysis of the partial density of states not only identifies the relevant transitions, but also reveals the origin of X-ray absorption fine structure (XAFS) around the edges. These results are of importance for the calibration of astronomical X-ray mirrors and gratings.