<title>Phase-sensitive data collection in x-ray crystallography using reference-beam diffraction</title>

Abstract

We present recent theoretical and instrumentation developments in phase-sensitive x-ray crystallography using a reference-beam data collection technique. The technique is based on the principle of three-beam or multiple-beam interference, but unlike the conventional method where interference profiles are measured one at a time, the reference-beam diffraction technique integrates three-beam diffraction into the popular oscillation method of data collection, and allows parallel recording of many three-beam interference profiles on an area detector simultaneously [1,2]. Complete interference profiles are measured by taking multiple oscillation exposures while stepping through the rocking curve of the reference reflection. Recent developments include a portable five-circle kappa diffractometer designed to be a part of an automated reference-beam oscillation setup, and a simplified three-beam diffraction theory using a distorted-wave approach that can be used in reference-beam data analyses to extract the reflection phases.