Fritz-Haber-Institut der Max-Planck-Gesellschaft

Department of Molecular Physics

Spectroscopy and chemistry of metal clusters and cluster complexes

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4th Ringberg meeting
on Molecular Physics
2009

Infrared Spectroscopy of Clusters

Rh4CO

Small metal particles are rapidly gaining importance in nanostructured material science and catalysis. The geometric and electronic structures of such small clusters differ from those of bulk material, and they can have surprising properties, as, for example, demonstrated by the catalytic activity of gold nanoparticles. We are focusing on the investigation of the relationships between chemical properties, structure and charge state for small metal and metal oxide clusters (containing typically less than 20 atoms) with the aim of better understanding heterogeneous catalytic reactions on a molecular level. Insights into the structural properties of the clusters and cluster complexes are obtained by infrared spectroscopy in combination with theoretical calculations.

Fragmentation upon irradiation with IR from FEL

Until now, most of the experiments are still conducted at the “Free Electron Laser for Infrared eXperiments“ (FELIX) in the Netherlands and since more recently the new FEL at the Fritz-Haber Institute. We exploit the intense IR radiation from the FEL to induce resonant multiple photon excitations in the clusters. The resulting hot clusters may dissociate or even ionize. Both processes can be detected via mass spectrometry. This allows to obtain the cluster-size specific vibrational spectra.

reconstructed VMI-PES of IrH at 532 nm

Another technique we apply to gas-phase molecules and clusters is photoelectron spectroscopy (PES). For this we have set up an experiment to investigate mass selected anions using velocity map imaging PES. In its high resolution variant, slow electron velocity map imaging (SEVI), where the electrons are produced by near-threshold photodetachment we obtain kinetic energy resolutions in the meV range, allowing for vibrationally resolved electron spectroscopy.

Literature:
Vibrational Spectroscopy of Strongly Bound Clusters P. Gruene, J. T. Lyon, and A. Fielicke, in Handbook of Nanophysics Vol. 2: Clusters and Fullerenes, K. Sattler (Ed.), Taylor & Francis (2010) pp. 9.1-9.14.
Vibrational Spectroscopy of Gas-Phase Clusters and Complexes K.R. Asmis, A. Fielicke, G. von Helden, and G. Meijer, in The Chemical Physics of Solid Surfaces: Vol. 12, Atomic Clusters: From Gas Phase to Deposited P. Woodruff (Ed.), Elsevier (2007) pp. 327-375.

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Address: Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany