New method for determining the phases of diffracted x rays

Ever since the discovery of x‐ray diffraction by Max von Laue in 1912, it has been recognized that there is a serious obstacle to determining the structure of a crystal from its x‐ray diffraction pattern: While it is not at all difficult to measure the intensity of the diffracted beam, it is not at all clear how to measure its phase. Over the years crystallographers have developed techniques to get around this problem—techniques that involve chemical substitution in the crystal, excitation of anomalous scattering by some of the atoms, or computational methods to establish the most probable sets of phases. In recent years it has become apparent that another technique, based on interference effects among diffracted beams, may become an extremely useful technique for the direct, experimental determination of the phases of diffracted x rays.