Regensburg 2007 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 13: Symposium: Ultrafast Nanooptics II
O 13.6: Vortrag
Montag, 26. März 2007, 16:45–17:00, H38
Influence of the interband transition on the optical properties of gold nanoparticles — •Frank Hubenthal, Nils Borg, Christian Hendrich, and Frank Träger — Universität Kassel, Institut für Physik and Center for Interdisciplinary Nanostructure Science and Technology, Heinrich-Plett-Str. 40, 34132 Kassel, Germany
We present systematic measurements of the ultrafast dephasing time T2 of surface plasmon resonances (SPRs) in gold nanoparticles (NPs) as a function of photon energy. The objective is to investigate the influence of the interband transition on the damping of the SPR, typically described by the damping parameter A. Gold NPs were prepared by deposition of thermal atoms followed by subsequent diffusion and nucleation, i.e. Volmer-Weber-growth. Thereafter, systematic measurements of T2 were carried out by persistent spectral hole burning. The most essential among the numerous results is the observation of an increased damping of the SPR at the onset of the interband transition. While the damping parameter A amounts to 0.20 nm/fs for photon energies below the onset of the interband transition at 1.85 eV, the damping increases to A = 0.32 nm/fs at 1.85 eV. For higher photon energies the contribution of the interband transition becomes the dominant damping mechanism, resulting in a reduction of A to as little as 0.15 nm/fs. The high A-Factor at 1.85 eV cannot be explained semiclassically by taking only the surface scattering of the oscillating electrons into account. In fact, we observe an increased Landau damping in Au NPs at the onset of the interband transition, which has not been identified before for all other photon energies.