A beam of zinc atoms reflected from a sodium chloride crystal is in part specularly reflected. The specular beam was investigated: (1) by measuring the velocity distribution of the atoms composing the specular beam; and (2) by examining the specular beam after reflection from a second crystal. A difference in angle of 22.5 between the two crystals does not greatly reduce the intensity of the specular beam. It is concluded that if velocity selection or a space-grating type of reflection of zinc is present it is not very pronounced.

Double reflection experiments of cadmium from sodium chloride crystals have been repeated and apparently evidence for both space and surface-grating phenomena found in certain cases. It is suggested that individual differences in crystals may be an important factor in causing these differences.

• Received 16 July 1930

DOI:https://doi.org/10.1103/PhysRev.36.893