Spectrally dependent locations of hot-spots in nanoparticle clusters

We study the optical response of clusters of metallic nanospheres in the electrostatic approximation, using a spherical harmonic representation of the electric field. Field enhancement and near field interactions between the spheres are investigated numerically. Symmetry properties of certain clusters give rise to highly localized maxima of the electric field, denoted hot spots. From numerical experiments performed at optical frequencies of the incident light, it is found that various geometrical configurations exhibit interesting phenomena; in particular, that hot spots move spatially around as a function of the frequency of the incident light. We present simulation results for the simplest nanoparticle cluster known to exhibit these interesting phenomena, namely, a regular octahedron. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim