Date of Award
Doctor of Philosophy
Physics and Astronomy
The extent to which x-ray extinction occurs in a crystal is determined by the perfection of the crystal. Those wavelengths which could be reflected by the lattice in a perfect crystal are extinguished by multiple reflections, resulting in a high absorption coefficient for the crystal. The imperfection of the surface decreases the possible number of these multiple reflections, thereby increasing the energy going to form the Laue patterns;Piezo electric oscillation of quartz, Rochelle salt and tourmaline crystals brings about as increase in the intensity of the Laue pattern formed by the reflection of x-rays passing the crystals. This effect is very noticeable for quartz, but it is not so pronounced in Rochelle salt and tourmaline. The oscillation of the crystal reduces the perfection of the lattice so that extinction is reduced and more energy passes through the crystal in both the secondary beams and the primary beam;Etching the surfaces of the crystal plates decreases their reflecting power for x-rays but also increases the strength of oscillation of the crystal. The effect on quartz is very pronounced, the effect of etching is overshadowed by the increased strength of oscillation, which results in a more intense pattern than for the non-oscillating crystal. The increased strength of oscillation distorts to a greater extent the structure of the crystal so that less of the energy is removed from the primary beam by reflection, and also increases enormously the efficiency of reflection.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Walter Alexander Fraser
Fraser, Walter Alexander, "X-ray extinction in piezo electric crystals " (1935). Retrospective Theses and Dissertations. 12953.