Optical diffraction techniques for interpreting X‐ray diffraction photographs of fiber structures

Abstract

AbstractThe classical interpretation of x‐ray diffraction patterns of single crystals is through Bragg's law and it leads to the notion that each “reflection” is a separate entity in a list of data. The adoption of the optical diffraction, or transform, approach leads to a much more physical view of the diffraction process in which the pattern is assessed as a whole. Studies of the Fraunhofer diffraction pattern in visible light of masks representing the unit crystal cell provide a means of testing the validity of trial structures. The particular value of this approach in fiber studies is that masks can be made to represent extremely complicated atomic arrangements and their patterns can be observed instantaneously. The key problem, is, of course, the preparation of the masks. The most versatile procedure would be to build a semi‐automated machine controlled by punched tape prepared on a computer. Design studies are in progress. Several interim methods, including photographic etching, are in use at the moment and various aspects of the interpretation of fiber photographs will be illustrated with diffraction patterns prepared from masks made in this way. Interpreting fiber photographs from the standpoint of their diffraction aspects rather than from a structural model may provide valuable complementary evidence to that produced in the more conventional way.