The distribution of mercury atoms scattered from NaCl, KCl, KBr and KI has been studied by means of an ionization gauge as a function of the angle of incidence and temperatures of scatterer and incident beam. The following facts are observed for the first three crystals: (1) There is a directed beam whose deviation from a specular position increases at smaller glancing angles. (2) The angle between the crystal surface and the direction of maximum intensity in the directed beam becomes less for lower crystal temperature and higher beam temperatures. (3) The relative number of atoms scattered at random increases with decrease in crystal temperature. (4) The directed beam becomes more sharply defined at lower crystal temperatures. Within the limits of error of the present experiments no discernible change is produced by rotation of the scattering crystal about an axis perpendicular to the plane of its face. The above facts are shown to be, qualitatively at least, consistent with a space-grating theory of reflection. In the case of KI the scattering was entirely random, i.e., according to the cosine law. This is also true for scattering by glass.

• Received 24 July 1931

DOI:https://doi.org/10.1103/PhysRev.38.977