title: Gold atoms and dimers on amorphous SiO(2): calculation of optical properties and cavity ringdown spectroscopy measurements.
abstract: We report on the optical absorption spectra of gold atoms and dimers deposited on amorphous silica in size-selected fashion. Experimental spectra were obtained by cavity ringdown spectroscopy. Issues on soft-landing, fragmentation, and thermal diffusion are discussed on the basis of the experimental results. In parallel, cluster and periodic supercell density functional theory (DFT) calculations were performed to model atoms and dimers trapped on various defect sites of amorphous silica. Optically allowed electronic transitions were calculated, and comparisons with the experimental spectra show that silicon dangling bonds [[triple bond]Si(.-)], nonbridging oxygen [[triple bond]Si-O(.-)], and the silanolate group [[triple bond]Si-O(-)] act as trapping centers for the gold particles. The results are not only important for understanding the chemical bonding of atoms and clusters on oxide surfaces, but they will also be of fundamental interest for photochemical studies of size-selected clusters on surfaces.
authors.affiliation: Dipartimento di Scienza dei Materiali, Universita di Milano-Bicocca, via R. Cozzi 53, I-20125 Milano, Italy.
authors.forename: Annalisa
authors.initials: A
authors.lastname: Del Vitto
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Pacchioni
authors.forename: Kok Hwa
authors.initials: KH
authors.lastname: Lim
authors.forename: Notker
authors.initials: N
authors.lastname: Rösch
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Antonietti
authors.forename: Marcin
authors.initials: M
authors.lastname: Michalski
authors.forename: Ulrich
authors.initials: U
authors.lastname: Heiz
authors.forename: Harold
authors.initials: H
authors.lastname: Jones