A STUDY OF THE SELF-ABSORPTION EFFECT IN THE FLUORESCENCE YIELD OF NIO AT THE OXYGEN K-EDGE

We demonstrate geometry-dependent self-absorption effects in the fluorescence yield photoabsorption spectra of bulk NiO. We observe a decrease of the atomic like smooth part of the data above the oxygen K edge and a damping of the EXAFS wiggles. For a cubic substance (NiO single crystal) self-absorption is studied systematically in the energy range above the O K absorption edge by varying the angle between the incident photons and the sample surface over a wide range. If self-absorption is not considered in the data analysis, the amplitudes of the EXAFS modulation can be damped significantly and the errors for coordination numbers can reach 50%.