Diffraction of partially coherent X-rays and the crystallographic phase problem.

This paper proposes a new physical method for the partial solution of the crystallographic phase problem by illuminating the crystal with an X-ray beam of limited coherence. The diffraction spots broaden and, if the coherence length of the incident beam is small enough in all three dimensions, the diffraction pattern becomes continuous. Independent information about the structure is then available both at the Bragg angles and at angles that do not satisfy the Bragg conditions. Under certain conditions, the total information is sufficient to solve the crystal structure ab initio. Two prescriptions for producing X-ray beams with limited coherence are given.