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International
Tables for Crystallography Volume F Crystallography of biological macromolecules Edited by M. G. Rossmann and E. Arnold © International Union of Crystallography 2006 |
International Tables for Crystallography (2006). Vol. F. ch. 9.1, p. 178
Section 9.1.5.1. Overview
a
National Cancer Institute, Brookhaven National Laboratory, NSLS, Building 725A-X9, Upton, NY 11973, USA, and bStructural Biology Laboratory, Department of Chemistry, University of York, York YO10 5DD, England |
The diffraction condition for a particular reflection is fulfilled when the corresponding reciprocal-lattice point lies on the surface of the Ewald sphere. If a stationary crystal is irradiated by the X-ray beam, only a few reflections will lie in the diffracting position. To record intensities of a larger number of reflections, either the size of the Ewald sphere or the crystal orientation has to be changed. The first option, with the use of non-monochromatic, or `white', radiation, is the basis of the Laue method (Chapter 8.2![[link]](/graphics/greenarr.gif)
). If the radiation is monochromatic, with a selected wavelength, the crystal has to be rotated during exposure to bring successive reflections into the diffraction condition.
Several different ways of rotating the crystal have been used in crystallographic practice. These range from rotation about a single axis to use of a three-axis cradle, depending on the detector and application.
