A semi-empirical absorption-correction technique for symmetric crystals in single-crystal X-ray crystallography. I

A new semi-empirical absorption-correction procedure is described, applicable to X-ray diffraction data collected on a four-circle diffractometer from a single crystal with at least one crystallographic twofold rotation symmetry. The technique is basically a modification of those procedures that make use of ψ-scan intensity variations and is primarily intended for biological macromolecular samples, although it is not limited to such samples. This is the first part of a two-part series and deals with the case wherein the symmetry axis is along the instrument φ axis and the data are collected in the bisecting mode.