Laue Patterns from Thick Crystals at Rest and Oscillating Piezoelectrically

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Abstract
Laue patterns have been observed for thick crystals of quartz and Rochelle salt oscillating piezoelectrically and for the same crystals as well as for calcite, rock-salt and other materials at rest. Patterns have been obtained when the crystalline faces were the natural cleavage surfaces and when they were polished and when etched by suitable solvents. Regular Bragg reflections have been observed and compared for a quartz crystal with polished face and for the same crystal with the face etched with hydrofluoric acid. In the Laue patterns, the individual spots show a multiple structure in every case. The inner spots are double in nature. For the crystal oscillating piezoelectrically or at rest with polished faces the doubling of each spot is radially symmetrical. For the crystal with etched faces and at rest the inner component of the double spot is the stronger particularly for those spots near the center. The Bragg reflection from a quartz crystal with etched face shows the absence of any layer with reduced extinction at the surface. Further elaboration of the Laue diffraction theory seems necessary to account for the multiple structure of the spots formed by an ideally perfect crystal.