Polarization effects in X-ray/matter interactions

The high brilliance of the synchrotron light make SRXRF more efficient and precise for element analysis than XRF performed with conventional X-ray tubes, allowing for measurements with a monochromatic beam. However, the really distinctive characteristic of the synchrotron beam is the high degree of polarization of the photons, which conditions the angular distribution of the scattered radiation. In SRXRF of thick thickness samples, the whole X-ray spectrum receives important contributions from multiple collisions of interactions like the photoelectric effect, and Rayleigh and Compton scattering, which depend differently on the polarization state of the incoming photons. The X-ray spectrum is formed essentially by three groups of multiple scattering contributions: pure scattering, pure photoelectric and mixed photoelectric-scattering. These groups are analyzed in this article, and their influence on the spectrum and the analytical method is discussed with recourse to a computational code based on a transport model for polarized photons. The influence of the polarization in SRXRF is discussed, stressing the importance of performing accurate spectrum calculations (including the polarization effects) for applications in trace element analysis. Copyright © 1996 by Marcel Dekker, Inc.