High-energy x-ray anomalous dispersion correction for silicon

Energy-dependent structure factors measured by Saka and Kato [Acta Crystallogr., Sect. A 43, 252 (1987); 43, 255 (1987)] for silicon are analyzed, and values of the real part of the anomalous dispersion correction term extracted for 12 wavelengths in the range 0.30.8 AìŠ with an estimated accuracy of a few millielectrons. This is the first experimental set of such data for wavelengths less than 0.56 AìŠ. The agreement with previous high-accuracy data for 0.56 and 0.71 AìŠ is very good. Comparison with nonrelativistic and relativistic theoretical calculations shows excellent agreement down to 0.4 AìŠ with very recent relativistic calculations including multipole and retardation terms. For shorter wavelengths a small deviation between theory and experiment is observed. Possible causes for this are discussed.