Frankfurt 2006 – wissenschaftliches Programm

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MO: Molekülphysik

MO 13: Molecular Clusters I

MO 13.4: Vortrag

Montag, 13. März 2006, 14:45–15:00, H10

Gas Phase Vibrational Spectroscopy of Bimetallic Oxide Cluster Anions — •E. Janssens^1,2, G. Santambrogio¹, M. Brümmer¹, L. Wöste¹, P. Lievens², J. Sauer³, G. Meijer⁴, and K.R. Asmis⁴ — ¹Institut für Experimentalphysik, F.U. Berlin, Arnimallee 14, 14195 Berlin — ²Laboratorium voor Vaste-Stoffysica en Magnetisme, K.U. Leuven, Celestijnenlaan 200 D, 3001 Leuven, Belgium — ³Institut für Chemie, H.U. Berlin, Unter den Linden 6, 10099 Berlin — ⁴Fritz-Haber Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin

Transition metal oxides on oxide surfaces play a central role in heterogeneous catalysis. However because of the complex interactions between the active sites and the support, the catalytic mechanisms are not completely known. Molecular beam studies on mass-selected particles under well controlled conditions can aid to understand these interesting systems. Here, we present the first systematic infrared study of bimetallic oxide clusters in the gas phase.
Mixed V_nTi_mO_p⁻ clusters are studied with IR multiphoton dissociation spectroscopy in the 500 to 1200 cm⁻¹ range and assigned on the basis of harmonic frequencies calculated with DFT. The clusters are produced in a dual laser vaporization source, stored in an ion trap, and irradiated with IR light of a free electron laser. The closed shell (V₂O₅)_n−1(VTiO₅)⁻ (n=2−4) clusters are shown to form caged structures similar to their isoelectronic monometallic counterparts, the neutral vanadium oxide clusters (V₂O₅)_n (n=2−4). Titanium-richer anions, V_4−nTi_nO₁₀⁻ (n=1−4), prefer to maintain the tetrahedral shape of V₄O₁₀ rather than pairing electrons, leading to a quartet ground state in Ti₄O₁₀⁻.