Berlin 2001 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 18: Poster: Polymer Blends, Heterogeneous Systems, Colloids and Nanoparticles, Interfaces, Polyelectrolytes

CPP 18.21: Poster

Wednesday, April 4, 2001, 12:30–15:00, AT1

Coupling of plasmon modes in metal nanoparticle pairs   — •T. Franzl, C. Sönnichsen, G. von Plessen, and J. Feldmann — Photonics and Optoelectronics Group, Physics Department and Center for Nanoscience (CeNS), University of Munich, Amalienstrasse 54, 80799 Muenchen, Germany

The particle plasmon resonances of two metallic nanoparticles in close vicinity to each other split into a longitudinal and a transverse mode. The longitudinal mode is shifted significantly to lower energies compared to the plasmon resonance of an isolated particle. In measurements on particle ensembles it is impossible to selectively excite one of the coupled plasmon modes if there is spectral overlap between the two resonances. However, by measuring scattering spectra of individual particle pairs with controlled polarization of the excitation light, we are able to address the modes separately. Our results on spherical silver nanoparticles with diameters of 60nm show mode splittings of up to 94nm or 470meV. In addition we are able to determine the inter-particle spacing using an atomic force microscope. The results are compared with theoretical calculations. Studying coupled plasmon resonances of particle pairs is an important step towards a deeper insight into the optical properties of larger aggregates and the understanding of the associated energy transfer and coupling processes.