Reconsideration of the wavelength dependence of extinction: a gamma-ray case.
The wavelength dependence of extinction has been re-examined by means of new gamma-ray diffraction data collected from NiF(2) at 0.0205, 0.0265 and 0.0392 A. The standard model of extinction has been confirmed and substantiated by experimentally accessible parameters such as the intrinsic mosaic width. The predicted kinematic limit values are in accordance with the results from charge-density analyses. The model proposed by Mathieson & Stevenson [Acta Cryst. (2002), A58, 185-189] leads to a purely phenomenological polynomial fit function. The extrapolated values are shown to be inconsistent with structure analyses based on extended gamma-ray data sets and cannot be recommended for use.
Hahn-Meitner-Institut, Glienicker Strasse 100, D-14109 Berlin, Germany. jauch@hmi.de
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