Saka Takashi
Daido University, 10-3 Takiharu-cho, Minami-ku, Nagoya, 457-8530, Japan.
Acta Crystallogr A Found Adv. 2018 Sep 1;74(Pt 5):586-594. doi: 10.1107/S2053273318009944.
The real part of the dispersion surface in X-ray dynamical diffraction in the Laue case for perfect crystals is analysed using a Riemann surface. In the conventional two-beam approximation, each branch or wing of the dispersion surface is specified by one sheet of the Riemann surface. The characteristic features of the dispersion surface are analytically revealed using four parameters, which are the real and imaginary parts of two quantities that specify the degree of departure from the exact Bragg condition and the reflection strength. The present analytical method is generally applicable, irrespective of the magnitudes of the parameters with no approximation. Characteristic features of the dispersion surface are also revealed by geometrical considerations with respect to the Riemann surface.
利用黎曼曲面分析了完美晶体劳厄情形下X射线动力学衍射中色散面的实部。在传统的双光束近似中，色散面的每个分支或侧翼由黎曼曲面的一张片来确定。利用四个参数解析地揭示了色散面的特征，这四个参数是两个量的实部和虚部，这两个量确定了偏离精确布拉格条件的程度和反射强度。本文的分析方法普遍适用，与参数大小无关，无需近似。通过对黎曼曲面的几何考虑也揭示了色散面的特征。
