Chemical interface damping of surface plasmon excitation in metal nanoparticles:: a study by persistent spectral hole burning

As demonstrated recently, persistent spectral hole burning in the optical spectra of metal nanoparticles makes possible the determination of the ultrafast dephasing time T-2 of surface plasmon excitation. Here, the influence of the chemical environment on the dephasing process is investigated under ultrahigh vacuum conditions by depositing an adsorbate on the nanoparticles. By comparing the optical spectra and the widths of the generated holes of the nanoparticles with and without adsorbate coverage, the influence of chemical interface damping on the dephasing process is examined. The potential of the novel procedure is demonstrated for silver nanoparticles on sapphire and quartz substrates using SO2 as the adsorbate. A drastic decrease of T-2 for the adsorbate-covered nanoparticles is observed and explained by dynamic charge transfer of electrons from the particles into and out of adsorbate states of the SO2 molecules.