On the intensities of electron diffraction rings

Abstract

The intensities of the rings formed when a beam of fast electrons is sent through a poly crystalline film were first studied by G. P. Thomson (1929) in the case of thin films of gold. The intensities were found to fit very well (Mott 1929) with those calculated theoretically on the assumption that the Laue theory held for scattering of electrons by the crystallites. Results also in accordance with the theory were obtained by Mark and Wierl (1930). A recent investigation by Ornstein and his collaborators (1938) on polycrystalline films of copper and silver have led to results diverging widely from the theoretical in the sense that if the (222) ring were fitted to the theoretical value the (111) ring, which is the strongest, had an intensity too low by a factor of two to three. It had also been pointed out by Kirchner (1932) that the amount of scattering by atoms of the heavy elements (Au, Ag) is so large that the Laue theory can hardly be expected to hold, and he discounted the significance of the agreement between theory and experiment.