Low-temperature resonance Raman scattering from iodide adsorbed on nanostructured silver surfaces

An overtone progression was observed in Raman scattering spectra from iodid e-modified, electrochemically roughened silver surfaces at low temperatures . Spectral intensities of the bands were found to vary with the degree of s urface roughening, whereas vibrational frequencies remained highly conserve d. Both surface-enhanced and resonance scattering phenomena contribute to o bserved band intensities when excited in the spectral region between 406 an d 415 nm. It is suggested that the progression originates from I-2-like spe cies that are formed on small silver clusters at low temperatures under irr adiation. This complex can be viewed as a supermolecule in which the electr onic resonance is determined by the size of the cluster and I-I stretch rep resents a normal mode of the molecule.