Charge-induced electromagnetic resonances in nanoparticles

Electromagnetic theories have reproduced the scattering properties of differently shaped particles and successfully been used to characterize numerous systems. However, certain anomalous features remain unexplained that include enhanced extinction when particles are much smaller than the wavelength. Here we explain these features exploiting recent research in electromagnetic scattering theories that suggests incorporating the effect of particle charge results in new physical outcomes that deviate appreciably from what is predicted by electromagnetic interaction from uncharged systems. For electrically charged particles, the resonant excitation of surface modes is governed by excess charges deposited on the particle surface. Charge effects become large when particles are small compared to the incident wavelength, and we show that the electrostatic approximation is not valid for modelling the electromagnetic interaction from such particles. Charge-induced resonances appear in such systems that can reproduce previously unexplained phenomena, for instance, amplified microwave attenuation observed in sandstorms. (copyright 2015 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)