Self-absorption correction strategy for fluorescence-yield soft x-ray near edge spectra

It is well known that fluorescence-yield x-ray absorption measurements of thick concentrated samples can exhibit severe spectral distortions due to the “self-absorption” effect. While reliable corrections for this effect have been described for the EXAFS region an accepted procedure does not exist for the XANES region, in which the distortions are more severe. This problem is of particular relevance in the soft X-ray region in which transmission measurements are usually impossible. We describe a procedure for the correction of XANES spectra for selfabsorption spectral distortions which is based on the scaling of the experimental spectrum to tabulated cross-sections. We apply the method to polarization-dependent O K-edge measurements in cubic NiO, in which no intrinsic polarization dependence is expected. The procedure is able to reduce by a factor of 3 the self-absorption distortions.