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MS: Massenspektrometrie

MS 9: Posterbeiträge

MS 9.11: Poster

Donnerstag, 16. März 2006, 16:30–18:30, Labsaal

Size effects and reactive behaviour of small mass-selected silver clusters in the presence of NO and CO — •Denisia M. Popolan¹, Sandra M. Lang^2,1, Jan Hagen², Liana D. Socaciu-Siebert², Ludger Wöste², and Thorsten M. Bernhardt¹ — ¹Abteilung Oberflächenchemie und Katalyse, Universität Ulm, 89069 Ulm — ²Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin

Although a large number of experiments were performed in the past, the catalytic reaction mechanisms at atomic level remain largely elusive. In this context, the investigation of small charged clusters in the gas phase might help to decipher the details of the catalytic reaction mechanisms. Nitric oxide plays an important role in many biological and chemical processes, it is however also liberated as toxic gas during combustion processes and responsible for the ozone production in urbanities due to their high reactive behavior in atmospheric environment. Silver particles have been proposed as catalyst for the reduction of NO to N₂ by carbon monoxide. In this contribution the reactivity of small silver cluster anions in the presence of NO and a mixture of NO with CO will be presented. The experimental procedure consists in storing the mass-selected cluster ions in an rf-octopole ion trap filled with buffer gas and small partial pressures of reactant gases. Product ion concentrations as a function of storage time enable the determination of reaction kinetics on free clusters. The decisive role of charge transfer in the NO bond breakage, NO oxidation, and the formation of free NO₂⁻ and N₂O₄⁻ ions, as well as N_xO_(y>x) ligands on the Ag_n⁻ clusters will be demonstrated.