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Anomalous Dispersion of X-rays in Crystallography

The Contribution of Resonance or Dispersion Effects to the Atomic Scattering Factors

S. Caticha-Ellis

Instituto de Fisica `Gleb Wataghin' Universidade Estadual de Campinas C.P. 1170 - Campinas - S.P. Brasil

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• Introduction
• Scattering by a Classical Dipole Oscillator
• The Atomic Scattering Factor. The Oscillator Strength
• The Oscillator Density
• Use of the Photoelectric Absorption Measurements
• The Imaginary Component ${\Delta}f^{\prime\prime}$
• References

Teaching Aims

To lay a foundation for the understanding of the phenomenon of anomalous dispersion and its significance and importance now that very accurate methods of measuring X-ray intensities are available.

Level

This is suitable as an introductory text in a postgraduate course designed for students who are already fairly well acquainted with X-ray crystallography.

Background Required

A fairly thorough knowledge of crystallography and of X-ray diffraction principles and techniques is really necessary for a proper understanding of this article.

Practical Resources

No specific resources are needed - though actual experience of X-ray photographs exhibiting anomalous dispersion effects would be an advantage.

Time Required for Teaching

This is a fairly `meaty' course which would require five or six hours for full discussion and assimilation.

Copyright © 1981, 1998 International Union of Crystallography