Light excitation of surface plasmons in metallic nanoparticle clusters can induce huge forces. We study such forces by using an electrodynamics approach, which fully incorporates the retardation effect. As two particles approach each other, the single-particle plasmons hybridize and split into attractive bonding modes and repulsive antibonding modes, which eventually evolve into an attractive band and a repulsive band. At an intensity of about 0.05 W / m 2 , the force can reach nano-Newtons and, hence, can dominate over other relevant interactions.

We show that the spatial decay of plasmons in a periodic metal-nanoparticle chain is composed of exponential and power-law decays. Our results show a high level of similarity between the absorptive and radiative decay channels. By analyzing the poles (and the corresponding residues) of the generating function for the lattice Green's function, we explain the details of the spatial decay profile. We also present an analytical formula for the decay profile.