Kossel diffraction and X-ray standing waves : two birds of one feather

Abstract
By virtue of the optical reciprocity theorem, Bragg-case Kossel diffraction in perfect crystals can be viewed as the reverse process of x-ray standing waves (XSW) in the sense that the location of the source of radiation and the point of detection are merely interchanged between the two. A method can then be devised to determine atomic positions in a crystal lattice by analyzing the profile of angularly resolved Kossel lines, yielding equivalent information as an analogous XSW experiment would. Technical aspects of this novel method are discussed and first experimental results involving Ge and Er:LiNbO₃ single crystal samples are presented, indicating that the equivalence between Kossel diffraction and XSW is indeed realized.