Bonding state energy of metal nanoparticle dimer and its dependence on nanosphere size and interparticle separation

Abstract

A study is conducted regarding the effects of particle size [Formula: see text] and interparticle separation [Formula: see text] on the electromagnetic (plasmon) coupling in a dimer of two identical metal nanospheres. The dimer states are modeled as the hybridized bonding and antibonding states of two isolated plasmon states, with the associated energies given in terms of the isolated plasmon energy ([Formula: see text], the coupling energy ([Formula: see text] and the overlap integral ([Formula: see text] of the constituent plasmonic fields. The resonance absorption energies of the isolated plasmon and the dimer in certain dielectric medium are calculated according to the Mie theory for incident light of parallel polarization along the dimer axis. The results are fitted with the bonding state energies of both Au and Ag nanosphere dimers for [Formula: see text] ranging within 10–20[Formula: see text]nm and x varied within [Formula: see text]–200[Formula: see text]nm in compliance with the restricted consideration of dipole absorption spectra. The excellent fits of the bonding state energies [Formula: see text] for the ranges of [Formula: see text] and [Formula: see text] variations are consistently achieved with [Formula: see text] around 0.99 by a single function of the form [Formula: see text] where [Formula: see text] and [Formula: see text] vary with the nanosphere materials and the surrounding media considered. This result suggests the possible relation of the best fitted functional form [Formula: see text] with the underlying physical mechanism.