Dresden 2011 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 10: Cluster

MO 10.3: Vortrag

Dienstag, 15. März 2011, 11:00–11:15, MER 02

Gas Phase Vibrational Spectroscopy of Cerium Oxide Cluster Cations — •Torsten Wende¹, Asbjörn Burow², Pieterjan Claes³, Marek Sierka², Gerard Meijer¹, Peter Lievens³, Joachim Sauer², and Knut R. Asmis¹ — ¹Fritz-Haber-Institut d. MPG, Berlin — ²Humboldt Universität Berlin — ³K.U. Leuven, Belgium

Cerium oxide is one of the most reactive rare earth metal oxides and play an important role in many catalytic applications. A key property of ceria (CeO₂) is the ability to release, store and transport oxygen ions which relies on the accommodation of electrons in localized f-orbitals. The theoretical description of localized Ce-4f states is a demanding task. Infrared photodissociation spectroscopy (IRPDS) of gas phase clusters can provide reliable data to test different DFT approaches.

Ce-containing clusters have not been spectroscopically studied in the gas phase yet. Here, we employ IRPDS combined with DFT calculations to characterize the structure of cationic cerium oxide clusters. Vibrational predissociation spectra of rare-gas tagged (CeO₂)_mCeO⁺ (m=0,1,...,4) and Ce_nO_2n−2⁺ (n=2,3) clusters are measured in the 400-1000 cm⁻¹ region. Structures containing a terminal Ce=O bond show a characteristic absorption band between 800-900 cm⁻¹. Larger clusters have common geometrical building units similar to bulk ceria leading to intense signals around 500 and 650 cm⁻¹. The results emphasize the importance of global optimization schemes and show that B3LYP does not always predict the correct global minimum structure.