Nonsymmetrical X-ray diffraction in a perfect rectangular t × l crystal. Extinction and absorption

Abstract

A theoretical investigation of diffraction in a rectangular t\times l crystal for nonsymmetrical coplanar scattering has been undertaken. The asymmetry in the scattering geometry, measured by an angle \gamma, causes different weights for the mixed Laue–Bragg contributions to the integrated power. Primary extinction and ordinary absorption are only moderately affected when the value of the geometrical parameter \zeta = (t/l)\tan\theta_{oh} \,\lt\, 1, \theta_{oh} being the Bragg angle. For increasing values of \zeta and \gamma the surface integration set-up for the Laue and Bragg regions is extensively changed, leading to pronounced effects. Analytical results for the normal absorption factor are presented.