Quasi-universality and scaling behaviour of three-wave X-ray interference in crystals: A novel way for the quantitative determination of X-ray reflection phases

A quasi-universal function describing the intensity distribution of three-w ave X-ray interaction in single crystals is derived for the first time from X-ray dynamical theory under the Bethe approximation for inversion-symmetr y related reflections. The intensity distributions of three-wave interferen ce can be scaled down to this dimensionless universal function with proper scaling factors. A newly derived intensity-ratio formula provides a new way of analyzing three-wave diffraction data for direct quantitative determina tion of X-ray reflection phases of complex systems involving macromolecules . (C) 1999 Elsevier Science B.V. All rights reserved.