Düsseldorf 2007 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 4: Atomic Clusters II
A 4.6: Vortrag
Montag, 19. März 2007, 15:30–15:45, 6G
Real-time spectroscopy of photo-chemical reactions on mass-selected clusters — •Marco Niemietz1, Kiichirou Koyasu1, Matthias Götz1, Markus Engelke1, Young Dok Kim2, and Gerd Ganteför1 — 1Department of Physics, University of Konstanz, 78457 Konstanz, Germany — 2Division of Nano Sciences and Department of Chemistry, Ewha Womans University, 120-750 Seoul, Korea
The surprising catalytic properties of small nanoparticles of noble metals [1,2] motivate the research on the reaction dynamics and photochemistry of such particles. Their interaction with oxygen has been suggested to be one of the most important elementary steps in heterogenous catalysis [3]. To shed light on the underlying mechanisms, we study the dynamics of reacted Ag and Au clusters by femtosecond time-resolved photoelectron spectroscopy.
The relaxation of photo-excited AgnO2− clusters with even number of atoms accompany ultrafast direct O2 photodesorption with an unusual high quantum yield compared to the bulk. In contrast, for the odd-numbered cluster Ag3O2−, a long-living excited state is observed, since O2 might be dissociatively chemisorbed here.
For Au2O−, the time-dependent evolution of the electronic states shows evidence for a photoactivated structural transition and subsequent fragmentation via several decay channels.
[1] A. Sanchez et al., J. Phys. Chem. A 103, 9573 (1999)
[2] D. C. Lim et al., Surf. Sci. 598, 96 (2005)
[3] T. S. Kim et al., J. Am. Chem. Soc. 125, 2018 (2003)