Collective surface modes of Ag single crystals

We calculate the electron-energy-loss spectra and the normal surface modes of the low-index faces of Ag single crystals. To this end we develop a model that accounts for the surface crystalline geometry and for both intraband and interband transitions. We obtain surface response functions that display a resonant structure due to face- and orientation-dependent modes, which lead to an anisotropy in the loss spectra for finite momentum transfers. Furthermore, they lead to a large anisotropy in the optical reflectance.