Wavelength-dependent measurements of extinction in an extended-face crystal of zinc selenide

The effect of extinction on Bijvoet ratios is demonstrated. It is suggested that an observed anomaly in the wavelength dependence of ZnSe Bijvoet ratios is due to the Borrmann effect. It is shown that wavelength-dependent studies of extinction may be used to obtain extinction parameters from relative intensity measurements without resorting to a refined scale factor.