Damping rates of surface plasmons for particles of size from nano- to micrometers; reduction of the nonradiative decay

Damping rates of multipolar, localized surface plasmons (SPs) of gold and silver nanospheres of radii up to 1000 nm were found with the tools of classical electrodynamics. The significant increase in damping rates followed by noteworthy decrease for larger particles takes place along with substantial red-shift of plasmon resonance frequencies as a function of particle size. We also introduced interface damping into our modeling, which substantially modifies the plasmon damping rates of smaller particles. We demonstrate unexpected reduction of the multipolar SP damping rates in certain size ranges. This effect can be explained by the suppression of the nonradiative decay channel as a result of the lost competition with the radiative channel. We show that experimental dipole damping rates [H. Baida, et al., Nano Lett. 9(10) (2009) 3463, and C. Sönnichsen, et al., Phys. Rev. Lett. 88 (2002) 077402], and the resulting resonance quality factors can be described in a consistent and straightforward way within our modeling extended to particle sizes still unavailable experimentally.

► We model plasmon damping rates up to the uncommonly large particles of 1000 nm. ► We demonstrate reduction of multipolar SP damping rates below its low size limit. ► We show that the radiative decay competes with the nonradiative processes. ► We model the quality Q-factor of SP multipolar resonances as a function of size. ► We confront our size characteristics with the experimental results of other authors.