Optical absorption of small metal particles with adsorbed dye coats.

The optical transmission spectrum of a discontinuous metal-island film is strongly affected by extremely thin layers (<1 monolayer) of dye adsorbate. Experimentally observed splitting and broadening of the plasma resonance of silver films with adsorbed rhodamine B and nile blue dyes can be described by an effective-medium calculation for the optical response: These observations and interpretations have important implications for understanding of surface-enhanced electromagnetic processes.