Berlin 2008 – scientific programme

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O: Fachverband Oberflächenphysik

O 12: Symposium: Size-Selected Clusters at Surfaces I
(Invited Speakers: Karl-Heinz Meiwes-Broer, Heinz Hövel, Thorsten Bernhardt)

O 12.3: Invited Talk (no funding)

Monday, February 25, 2008, 14:30–15:00, MA 005

Femtosecond laser spectroscopy of clusters at surfaces — •Thorsten M. Bernhardt — Institut für Oberflächenchemie und Katalyse, Universität Ulm, 89069 Ulm, Germany

Femtosecond two photon photoemission spectroscopy is employed to investigate the electronic structure of ultra-thin magnesium oxide films and of mass-selected clusters deposited onto this substrate. Distinct changes in the electronic structure of these films induced by oxygen vacancy defects and by metal cluster deposition are identified in the photoemission spectra and help to elucidate the origin of the observed catalytic activity of supported cluster nano-systems. Furthermore, in a new experimental approach, time-of-flight mass spectrometry in conjunction with femtosecond resonance-enhanced multiphoton ionization is used to directly monitor the chemical reaction dynamics of adsorbate molecules. This new method enables the distinction of different reaction pathways through direct real-time monitoring of the mass and the kinetic energy of reaction products and intermediates.