Photoelectric scattering from an X-ray interference field

The influence of different multipole terms on the photoelectric scattering process stimulated by an X-ray interference field which is generated by two plane, coherent waves is discussed. The contributions of dipole and quadrupole terms are analyzed starting with the model of a single atom within the X-ray standing wave field which is then generalized for a distribution of atoms within the interference field. We obtain solutions for the angular integrated (e.g. fluorescence) and differential cross-sections (e.g. angular resolved photoemission). Particular strong effects due to the presence of two coherent waves are expected for the differential cross-sections. It is shown, that each multipole term shows a different dependence on the polarization vectors (sigma-polarization, pi-polarization) and wavevectors of the direct and diffracted beam. We outline how multipole contributions can be determined by an X-ray standing wave measurement. (C) 1999 Elsevier Science Ltd. All rights reserved.