Long-Range Electron-Phonon Coupling at Metal Surfaces

Long-range scattering of slow electrons by phonon excitations at flat and clean Cu(100) and Ni(100) surfaces has been observed in high-resolution electron-energy-loss measurements. We show that the strength of this electron-phonon coupling derives from the oscillatory response of the electrons at the metal surface. We have evaluated the electron-scattering cross section within the jellium model for the electron response and find excellent agreement with the experimental results.