Plasmonic excitations in noble metals: The case of Ag

The delicate interplay between plasmonic excitations and interband transiti ons in noble metals is described by means of ab initio calculations and a s imple model in which the conduction electron plasmon is coupled to the cont inuum of electron-hole pairs. Band-structure effects, especially the energy at which the excitation of the d-like bands takes place, determine the exi stence of a threshold plasmonic mode, which manifests itself in Ag as a sha rp resonance experimentally observed at 3.8 eV. However, such a resonance d oes not appear in the spectra of the other noble metals. Here this differen t behavior is also analyzed, and an explanation is provided.