Reflection and Diffraction of Slow Electrons from Single Crystals of Tungsten

Measurements have been made of the elastic reflection coefficient and total secondary electron coefficient for electrons with energies from 1-206 eV incident normally on single crystals of tungsten (112), (100), and (110). The apparatus permitted visual observation of the full diffraction pattern in the same energy range. Ultra-high vacuum techniques were used. The major features of the elastic reflection coefficient for incident energies below 20 eV were found experimentally to be associated with the specularly reflected or 0-0 diffraction beam. A model based on superposition of atomic scattering was found to give a better over-all description of the observations than a model based on a potential varying only along the normal to the crystal.