High-Resolution Electron Energy Loss Spectroscopy of Cs Vibration on the Ru (0001) Surface

By using a newly implemented high-resolution electron energy loss spectrometer with better resolution, a new loss at a energy near to double energy of the Cs-Ru stretching vibration, and its dependence on Cs coverage for Cs overlayer on Ru (0001) were observed. Since the energy is slightly smaller than the double energy of the Cs-Ru vibration (intrinsic loss), overtone excitation must be responsible for this new loss observed, but two-phonon process is not excluded.