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Forbidden X-ray wavefields of three-beam Bragg reflections from thick crystals
X R Huang1, M Dudley, J Y Zhao
1Department of Materials Science and Engineering, State University of New York at Stony Brook, Stony Brook, New York 11794, USA. xiahuang@ms.cc.sunysb.edu
Acta Crystallographica. Section A, Foundations of Crystallography
|January 11, 2000
Summary
Forbidden wavefields in thick-crystal Bragg reflections are clarified. The study reveals that wavefield excitation in three-beam diffraction can be predicted using the two-beam criterion, simplifying analysis of crystal diffraction processes.
Area of Science:
- Condensed Matter Physics
- Crystallography
- Materials Science
Background:
- Understanding wavefield behavior in thick crystals is crucial for X-ray diffraction analysis.
- Forbidden reflections present unique challenges in interpreting diffraction patterns.
- Existing models may not fully capture the complexities of multi-beam diffraction.
Purpose of the Study:
- To analyze the forbidden wavefields in three-beam diffraction from thick crystals.
- To elucidate the underlying mechanisms of three-beam Bragg reflections.
- To establish a predictive framework for wavefield excitation states.
Main Methods:
- Detailed analysis of the three-beam diffraction dispersion surface.
- Asymptotic transition analysis between two- and three-beam diffraction.
- Application of the two-beam criterion to determine wavefield excitation.
Main Results:
- Wavefield excitation states in three-beam diffraction can be accurately determined by the two-beam criterion.
- Bragg-case three-beam diffraction exhibits distinct mode processes based on geometry (four-mode for Bragg-Laue, two-mode for Bragg-Bragg).
- Amplitudes of excited wavefields are fully determined by entrance boundary conditions.
Conclusions:
- The study provides a clear illustration of the intrinsic mechanisms governing three-beam Bragg reflections.
- The findings simplify the understanding and prediction of wavefield behavior in thick-crystal diffraction.
- This work offers a refined approach to analyzing complex X-ray diffraction phenomena.