Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 34: Particles and clusters II

O 34.4: Talk

Thursday, March 30, 2006, 12:00–12:15, WIL A317

Radiation damping of plasmons in metal nanoparticle pairs — •Christian Dahmen, Benjamin Schmidt, and Gero von Plessen — Nanostructure Optics Group, I. Physikalisches Institut (IA), RWTH Aachen, 52056 Aachen

The optical properties of electromagnetically coupled metal nanoparticles have received much interest. This interest is partially fuelled by the large local-field enhancement near coupled nanoparticles, which plays an important role in surface-enhanced Raman scattering. Another point of interest are the spectral properties of the coupled particle-plasmon resonances. They show large frequency shifts when the particle spacing is sufficiently small for near-field coupling to occur. Less attention has been devoted to the issue of radiation damping in coupled nanoparticles. Here we calculate the radiation damping rates of plasmon resonances in metal nanoparticle pairs using Generalized Mie theory, which takes retardation effects into full account. The radiation damping of the coupled particle-plasmon mode alternates between superradiative and subradiative behavior when the partice spacing is varied. The damping thus depends on the phase difference between the dipole of one particle and the field scattered by the other particle. At small particle spacings where near-field coupling sets in, the radiation damping rate lies far below that of an isolated particle. This reduction of radiation damping implies a reduced dephasing of the coupled plasmon mode and thus tends to increase the local field enhancement in the space between the particles.