Generalized extinction in bipyramidal crystals

The generalized extinction factors for a set of strong reflections as a function of wavelength are obtained by indirect measurements. The experiments are performed on a crystalline system that satisfies the geometrical requirements imposed by theoretical models developed for a finite perfect crystal. With increased perfection, represented by a reduction in the width of the mosaic distribution function from three to one thousandth of a degree, the experiments give results that approach the predictions from the theory. The present procedure utilizes measurements of the integrated diffracted power of a weak reflection for scaling the strong reflections, hence non-measurable wavelength-dependent factors are assumed to be eliminated.