Polarized X-ray Absorption. Quantitative Determination by Fluorescence Measurements

Abstract

For non-cubic crystals, polarized X-ray absorption due to anisotropic anomalous scattering (AAS) occurring in the vicinity of absorption edges can be determined, both qualitatively and quantitatively, from polarized fluorescence measurements. For crystals exhibiting `large' faces, a method is presented that allows the simultaneous determination of all absorption-tensor elements from a single-crystal rotation experiment. Energy variation included, the method may be used for single-crystal polarized absorption and fluorescence spectroscopy. Depending on the crystal system and the face investigated, the experimental set-up can require a tilt of the polarization direction(s) against the plane of measurement as well as a precession of the crystal face normal about the rotation axis Ψ. For all systems except triclinic, the experimental conditions are discussed and fluorescence intensity functions IF(Ψ) are developed and illustrated by model calculations.