Laue Diffraction

Abstract

When a stationary crystal is illuminated with X-rays from a continuous range of wavelengths (polychromatic or “white” radiation), a Laue diffraction pattern is produced. The very first X-ray diffraction pictures of a crystal were in fact obtained in this way by Friedrich, Knipping, and Laue in 1912. However, since then, monochromatic beams were used nearly exclusively in X-ray crystal structure determinations. This is due to the fundamental problem that a single Laue diffraction spot can contain reflections from a set of parallel planes with different d/n, where d is the interplanar distance and n is an integer. These spots are multiples instead of singles. This is easily explained by Bragg’s law: