On the determination of phases of a noncentrosymmetric crystal by the anomalous dispersion method

Abstract

It is commonly understood that the use of the anomalous-dispersion effect with a noncentrosymmetric crystal leads to the solution of the phase angle with a twofold ambiguity. It is pointed out that, with x-rays commonly used in experiments, the solution to the phase angle can be given, as a first approximation, as a single solution. When only one type of anomalous scatterer exists in the structure, such a solution can be represented as a tangent formula. The test of the formula in an actual case is presented. The above tangent formula takes an exact form when (a) additional data from isomorphous crystals are also available and (b) intensity measurements are made at two different wavelengths.