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Anomalous Scattering of Polarized X-Rays

Published online by Cambridge University Press:  21 February 2011

David H. Templeton  and
Lieselotte K. Templeton
David H. Templeton
Affiliation:
University of California, Department of Chemistry, Berkeley, CA 94720
Lieselotte K. Templeton
Affiliation:
University of California, Department of Chemistry, Berkeley, CA 94720
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Abstract

Some elements in some chemical states exhibit strong dichroism and birefringence near x-ray absorption edges. The atomic scattering factor is a complex tensor. This polarization anisotropy has profound effects on the transmission and scattering of x-rays even when the incident radiation is unpolarized. The linear polarization of synchrotron radiation makes it easier to study the effects and to use them for new methods of structure determination. Several of these anomalous scattering tensors have been measured by absorption spectroscopy and in diffraction experiments. New polarization terms enter the calculation of diffraction intensities, with interesting consequences. Reflections forbidden by a screw-axis rule are observed in sodium bromate near the Br K edge and permit direct observation of the structure factor phases of their second order reflections. This technique is a method of selective diffraction in which atoms of single element in a single chemical state contribute to the signal, and it can reveal their positions with precision. These effects can be a handicap for some applications of near-edge anomalous scattering in the study structures of crystals and amorphous materials.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 143: Symposium V – Synchrotron Radiation in Materials Research , 1988 , 177
Copyright
Copyright © Materials Research Society 1989

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