Gold Atoms and Dimers on Amorphous SiO_2:Calculation of Optical Properties and Cavity Ringdown Spectroscopy Measurements

摘要

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 [ident to Si~(centre dot)],nonbridging oxygen [ident to Si-O~(centre dot)],and the silanolate group [ident toSi-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.