POLARIZATION EFFECTS IN X-RAY PHOTON DIFFUSION

Polarization effects in x-ray spectrometry are explained with recourse to transport theory. Intensity contributions from multiple-scattering terms of the Rayleigh and Compton effects calculated with two models, one representing rigorously the polarization state (vector model) and the other approximating the effects of polarization by considering always the same average state (scalar model), are compared to show the influence of polarization in a practical way. It is shown that using average polarization represents a first-order approximation valid for unpolarized sources. As a paradigmatic example it is shown that the full account of polarization, for the case of a sample irradiated with an unpolarized x-ray source (i.e. x-ray tube), increases the estimated intensity of the multiple-scattering background without modifying the intensity of the first-order term. The effect of polarization is zero of can be neglected in those scattering chains which contain at least one photoelectric effect. In contrast, it must be considered to correct the computation of the continuous background under the Compton peak, due to collision events of the Rayleigh and Compton effects.