Oxidation-Induced Surface Plasmon Band Fragmentation in Silver Clusters

International audienceThe optical absorption of silver clusters is characterized by a strong plasmon band. However, most of the experimental photoabsorption measurements are performed on clusters interacting with a surrounding media, which can induce oxidation processes and possibly modify the optical properties. Here, we investigate the effects of oxygen adsorption onto the electronic structure and the optical properties of silver Ag$_{n}$ ($n$ = 8, 20, 38) clusters by using a well-established methodology based on the time-dependent density functional theory (TDDFT). The presence of oxygen atoms on the silver cluster is found to induce fragmentation of the plasmon resonance that can lead to its disappearance and the onset of many excitations having a low plasmonic character. The broadening of the plasmon band is shown to depend not only on the number of oxygen atoms but also on their positions with respect to the cluster. The interaction of Ag$_{8}$ clusters with molecular O$_{2}$ is also examined. Our study can be used to analyze experimental measurements related to oxygen chemisorption or physisorption on metal clusters and can also be considered as a first step to model optical properties of noble metal nanoclusters embedded in oxide matrices