Numerical determination of a true absorption spectrum from grazing-incidence fluorescence EXAFS

The fluorescence EXAFS spectra, measured at a grazing incidence angle larger than the critical angle for total reflection, were examined to test a numerical conversion from the distorted fluorescence data to the 'true' absorption spectra, achieving a reliable transferability between the transmission and the fluorescence data. Under various entrance and exit angles, full numerical corrections were made in terms of the sample's self-absorption, the measurement geometry, and the energy dependent efficiency function of the I,, ionization chamber detector. Particularly, a numerical code was developed for the x-ray fluorescence geometry configured without a scattering discrimination filter. For an illustration of glancing-angle fluorescence EXAFS spectra, we performed an in-situ measurement for the thick porous nickel specimens undergoing a heated-air surface oxidation process.