On the Effect of a Secondary Structure upon the Interference of X-rays

Laue's dynamic theory of x-ray interference is shown to be applicable, with only a few minor changes, to crystals having a very general type of secondary structure. It is thus applied for the purpose of obtaining a quantitative estimate of the effect of such a structure upon the nature of the x-ray interference maxima. The estimate is relative insofar as it compares the intensities of respectively the "secondarily" and the "primarily" reflected interference beams and applies only in the region where the latter have been, or can be observed. In this region the "two-dimensional lattice" type of secondary structure is found to give rise to a fine structure which, with the present insufficient resolving power, would be manifested experimentally as a weak, diffuse background. The secondary structure of this type produces no broadening of the primary lines. The existence of this type of structure, therefore, is not inconsistent with the sharpness of the interference maxima obtained from such crystals as calcite, and a possible objection to the existence of the secondary structure in such crystals is removed. The extinction effect is briefly considered, but absorption is not taken into account, except with a few qualitative remarks