Photoinduced luminescence from the noble metals and its enhancement on roughened surfaces

Single-photon- and multiphoton-induced luminescence spectra were obtained from clean samples of silver, copper, and gold with both smooth and rough surfaces. The spectra reveal new features which are correlated with interband transitions at selected symmetry points in the Brillouin zone. Calculating luminescence spectra based on simplified models of the band structures of the noble metals and taking into account the Fresnel local-field corrections, we find qualitative agreement with the observed spectra from smooth samples. The agreement between theory and experiment is less satisfactory for rough samples. The influence of surface roughness on the luminescence is largely attributable to local-field enhancement in the rough surface protrusions.