Effects of a General X-ray Polarization in Multiple-Beam Bragg Diffraction

The formalism of the N-beam dynamical theory of X-ray diffraction is extended to include all possible incident and diffracted polarizations. With this new formalism it is shown that the intensity of a simultaneously excited Bragg reflection can be described through a polarization density matrix that involves the Stokes-Poincar6 parameters. In particular, the multibeam diffracted intensity is sensitive to the circularly polarized component in the incident beam and the structure-factor phases of the diffracting crystal. Experimental results on the GaAs 442 and Ge 333 reflections confirm the theoretical calculations. © 1993 International Union of Crystallography Printed in Great Britain all rights reserved This kind of measurement can provide useful acentric phase information and can also be used for circular X-ray polarimetry. Another feature of N-beam diffraction is its ability to turn a linear polarization into an elliptical polarization, which means it can be used as an X-ray phase plate.