Frequency modulated X-ray diffraction I. Determination of partial structure factors

It is shown that when the frequency of incident X-rays is tuned just below an absorption edge of a particular element in a multi-element sample, the derivative of the scattered intensity with respect to the frequency of the X-rays is dominated by the interference of X-rays about this element. Frequency modulated X-ray diffraction should permit certain partial structure factors to be determined simply with a sensitivity orders of magnitude greater than techniques used previously. This technique should yield at least the same information that X-ray absorption (EXAFS) techniques are supposed to provide, but with fewer complications.