Electron Reflection Coefficient at Zero Energy. I. Experiments

The zero-energy reflection coefficient of electrons at a freshly evaporated silver surface has been measured to be 7%±1%. The coefficient rises linearly with 39% e${\mathrm{V}}^{-1\mathrm{}}$ above zero energy. In the experiments, particular care is taken that only those electrons which have actually interacted with the surface are counted; those which have been reflected by the applied field without interaction with the surface are not counted. This is accomplished by (1) use of a total-energy spectrometer, and (2) simultaneous recording of the energy spectrum and target current. Therefore, the reflection coefficient determined is essentially that for orthogonal incidence. The experimental method is critically discussed. In Sec. VI, the linear rise of reflection immediately above zero energy is attributed to atomic scattering at the surface. The reflection coefficient at zero energy can be fully explained by the patch-effect theory presented in paper II.