Theory of the Use of More Than Two Successive X-Ray Crystal Reflections to Obtain Increased Resolving Power

Abstract

If an x-ray beam is selectively reflected from more than two crystal surfaces in succession it is shown in this paper by a simple method of graphical analysis that it should be possible to obtain resolving power considerably superior to the best obtainable with present two crystal x-ray spectrometers. This extension and generalization of the two crystal spectrometer principle in one of its forms (the three crystal spectrometer) should permit the study of the asymmetric diffraction patterns predicted by the theory of Prins but heretofore considered to be completely beyond experimental investigation. In another form (the four crystal spectrometer) a distinct improvement in spectral resolving power is anticipated. The new method of graphical analysis invented for the purpose of discussing these more complicated cases of polycrystalline x-ray reflection is conspicuously useful and clear as a help to understanding the two crystal spectrometer also. An experimental test of these new methods is now in progress.