Mie Scattering by a Charged Dielectric Particle

Abstract

We study for a dielectric particle the effect of surplus electrons on the anomalous scattering of light arising from the transverse optical phonon resonance in the particle's dielectric function. Excess electrons affect the polarizability of the particle by their phonon-limited conductivity, either in a surface layer (negative electron affinity) or the conduction band (positive electron affinity). We show that surplus electrons shift an extinction resonance in the infrared. This offers an optical way to measure the charge of the particle and to use it in a plasma as a minimally invasive electric probe.

Optical signatures of electrically charged particles: Fundamental problems and solutions

“…Eqs. (1)-(2) and (4)- (5) have been presented by Bohren and Hunt [6], while Eq. (3) has been presented by Klačka and Kocifaj [7].…”

“…Although the optical properties of neutral particles were studied intensively in the last decades, the effect of surface charges on the electromagnetic scattering has received only minor consideration [3][4][5]. The fundamentals of scattering theories for charged systems date back to Bohren and Hunt [6] who introduced an excess charge surface conductivity independent of position on a spherical particle.…”

Measuring the plasma-wall charge by infrared spectroscopy

“…Using the memory function approach of ref. 16 , the bulk conductivity σ b determining α P can be calculated as…”

The electric field in sandstorm can strongly affect the sand׳s scattering properties

“…Some theoretical models and various numerical techniques have been found to predict the optical properties of particles [3,4], but most of them have neglected the effects of the environment factors, except for the environmental humidity [5] and the adhesion of mineral and soot aerosols [6,7]. However, most particles of interest in astrophysics and atmospheric sciences are charged [8][9][10][11][12], and those electrified particles not only enhance the attenuation of incident EM wave [13][14][15][16][17][18][19][20], but also generate a strong Electrostatic field (signed as E-field for short). For example, the charged sands or dusts can produce a strong E-field in the air [21][22][23][24][25][26], and the maximal intensity can reach up to 200 kV/m [27,28].…”