Polarized dispersion, glide-rule-forbidden reflections and phase determination in barium bromate monohydrate

Reflections forbidden by a glide-plane rule are observed in diffraction experiments with a crystal of barium bromate monohydrate using linearly polarized synchrotron radiation with wavelength near the bromine K-absorption edge. Their intensities change with azimuth in agreement with equations derived using a tensor model of the anomalous scattering of the bromate ion and are consistent in scale with earlier measurements of that tensor in sodium bromate. The intensity of each forbidden h0l reflection gives the magnitude and phase of the bromine part of the structure factor of the allowed 2h,0,2l reflection. The x and z coordinates of the Br atom determined from such data for 11 reflections are within 0.02 A of those from two crystal structure determinations.