Electromagnetic resonances observed in small, charged particles

Abstract

When a particle is charged, electrons can move freely along its surface and influence its optical properties in the same way as a thin, nonuniform metallic layer. These electrons contribute to scattering phenomena, including resonances. We model the light scattering from charged particles and demonstrate that these resonances result from excitation of an anti-symmetric surface plasmon at the layer interfaces. The modeling explains suppression of absorption when the size of the charged particle decreases, as well as differences in the light-scattering efficiencies of as much as a factor of 2 that occur before and after the resonance. These light-scattering properties must be taken into consideration when performing remote-sensing studies of charged particles, like those in the interstellar medium and dust storms.