Reflection of Metallic Atoms from Alkali Halide Crystals

The scattering of molecular beams of mercury from crystals of lithium fluoride, lithium chloride, sodium fluoride, and potassium iodide has been studied as a function of crystal and beam temperatures. A similar study has been made of the scattering of a molecular beam of cadmium from sodium chloride crystals. In all cases a quasispecular beam of the type reported by Zahl and Ellett (Phys. Rev. 38, 977 (1931)) for other alkali halide crystals was observed, with the same characteristic temperature changes. Former failures to detect a directed beam in the case of mercury scattered from potassium iodide were shown to have been due to moisture on the crystal surface. The relative number of atoms in the directed beam has been found to decrease with time at low crystal temperatures.