Dynamics of the fragmentation and ionization of free metal clusters by mild femtosesond laser pulses
Final Report Abstract
The original goal of this project was a combined experimental and theoretical study of the electronic and nuclear dynamics of metal cluster in fs-laser fields, with an emphasis on field amplification effects produced by the collective electron excitation. While this goal was not fully accomplished within the duration of the project, a wealth of new results was obtained already by the many preliminary experiments and calculations done. Measuring angle resolved photoelectron spectra of cold, size-selected sodium clusters for the first time demonstrated that these systems exhibit surprisingly clear superatom behaviour. The angular distributions of the photoelectrons allow one to identify the approximate angular momentum of their initial states, which not only yields strong support for the simple free electron model description of the electronic structure of sodium clusters, but also demonstrates that electron emission out of sodium clusters is a fully coherent process. In the theoretical studies structure and dynamics of gold clusters were elucidated. The relation between geometry, electronic structure and chemical reactivity was unravelled for the size range 15-24; also here electron shell effects were shown to play an important role. Furthermore a new type of cluster phase transition, a 2D-3D liquid-liquid transition, was found for gold clusters with 11-14 atoms. Such transitions have to be taken into account in the discussion of the formation process of these clusters, as they might lead to the preferential formation of metastable, non-ground-state structures.
Publications
- Liquid-Liquid Phase Coexistence in Gold Clusters: 2D or not 2D? Phys. Rev. Lett. 98, 015701 (2007)
P. Koskinen, H. Häkkinen , B. Huber, B. v. Issendorff, M. Moseler
- Size-dependent Structural Evolution and Chemical Reactivity of Gold Clusters. Chem. Phys. Chem. 8, 157 (2007)
B. Yoon, P. Koskinen, B. Huber, O. Kostko, B. von Issendorff, H. Häkkinen, M. Moseler and U. Landman
- Probing the Angular Momentum Character of the Valence Orbitals of Free Sodium Nanoclusters. Science 323, 1323 (2009)
C. Bartels, C. Hock, J. Huwer, R. Kuhnen, J. Schwöbel, B. von Issendorff
