title: Reactivity Control of Rhodium Cluster Ions by Alloying with Tantalum Atoms.
abstract: Gas phase, bielement rhodium and tantalum clusters, RhnTam(+) (n + m = 6), were prepared by the double laser ablation of Rh and Ta rods in He carrier gas. The clusters were introduced into a reaction gas cell filled with nitric oxide (NO) diluted with He and were subjected to collisions with NO and He at room temperature. The product species were observed by mass spectrometry, demonstrating that the NO molecules were sequentially adsorbed on the RhnTam(+) clusters to form RhnTam(+)NxOx (x = 1, 2, 3, ...) species. In addition, oxide clusters, RhnTam(+)O2, were also observed, suggesting that the NO molecules were dissociatively adsorbed on the cluster, the N atoms migrated on the surface to form N2, and the N2 molecules were released from RhnTam(+)N2O2. The reactivity, leading to oxide formation, was composition dependent: oxide clusters were dominantly formed for the bielement clusters containing both Rh and Ta atoms, whereas such clusters were hardly formed for the single-element Rhn(+) and Tam(+) clusters. DFT calculations indicated that the Ta atoms induce dissociation of NO on the clusters by lowering the dissociation energy, whereas the Rh atoms enable release of N2 by lowering the binding energy of the N atoms on the clusters.
authors.affiliation: Department of Basic Science, School of Arts and Sciences, The University of Tokyo , Komaba, Meguro, Tokyo 153-8902, Japan.
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Mafuné
authors.affiliation: Department of Basic Science, School of Arts and Sciences, The University of Tokyo , Komaba, Meguro, Tokyo 153-8902, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Tawaraya
authors.affiliation: Department of Basic Science, School of Arts and Sciences, The University of Tokyo , Komaba, Meguro, Tokyo 153-8902, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kudoh