Oxidation of CO and NO on Composition-Selected Cerium Oxide Cluster Cations

The collisional reactions of composition-selected cerium oxide cluster cations, Ce_<i>n</i>O_<i>m</i>⁺ (<i>n</i> = 2–6; <i>m</i> ≤ 2<i>n</i>), with CO and NO have been investigated under single collision conditions using a tandem mass spectrometer. At near-thermal energy, oxidation of CO and NO is observed only for the stoichiometric clusters, Ce_<i>n</i>O_2<i>n</i>⁺ (<i>n</i> = 3–5), and the cross sections for the NO oxidation are found to be larger than those for the CO oxidation. In addition, the collision-energy dependence of the reaction cross sections reveals that the CO oxidation has a small activation barrier, whereas the NO oxidation is a barrierless process. These experimental findings are supported by density functional theory calculations