title: Cooperative effects in the activation of molecular oxygen by anionic silver clusters.
abstract: A novel size dependence in the adsorption reaction of multiple O2 molecules onto anionic silver clusters Agn- (n = 1-5) is revealed by gas-phase reaction studies in an rf-ion trap. Ab initio theoretical modeling based on DFT method provides insight into the reaction mechanism and finds cooperative electronic and structural effects to be responsible for the size selective reactivity of Agn- clusters toward one or more O2. In particular, Agn- clusters with odd n have paired electrons and therefore bind one O2 only weakly, but they are simultaneously activated to adsorb a strongly bound second oxygen molecule. For the clusters Ag3O4- and Ag5O4-, this cooperative effect results in a superoxo-like, doubly bound O2 subunit with potentially high activity in catalytic silver cluster oxidation processes.
authors.affiliation: Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany. tbernhar@physik.fu-berlin.de
authors.forename: Jan
authors.initials: J
authors.lastname: Hagen
authors.forename: Liana D
authors.initials: LD
authors.lastname: Socaciu
authors.forename: Jérôme
authors.initials: J
authors.lastname: Le Roux
authors.forename: Denisia
authors.initials: D
authors.lastname: Popolan
authors.forename: Thorsten M
authors.initials: TM
authors.lastname: Bernhardt
authors.forename: Ludger
authors.initials: L
authors.lastname: Wöste
authors.forename: Roland
authors.initials: R
authors.lastname: Mitrić
authors.forename: Holger
authors.initials: H
authors.lastname: Noack
authors.forename: Vlasta
authors.initials: V
authors.lastname: Bonacić-Koutecký