Optical signatures of the Charge of a Dielectric Particle in a Plasma

TL;DR

This paper investigates how the negative charge of dielectric particles in plasma affects their light scattering properties, revealing charge-dependent optical signatures that could enable non-invasive charge measurements.

Contribution

It introduces a detailed analysis of charge effects on light scattering by dielectric particles with optical phonon resonances, highlighting new optical signatures related to particle charge.

Findings

Charge increases extinction efficiency at low frequencies.

Extinction resonance shifts above the transverse optical phonon frequency.

Polarization angles vary rapidly over the resonance.

Abstract

With an eye on dust particles immersed into an ionized gas, we study the effect of a negative charge on the scattering of light by a dielectric particle with a strong transverse optical phonon resonance in the dielectric constant. Surplus electrons alter the scattering behavior of the particle by their phonon limited conductivity in the surface layer (negative electron affinity) or in the bulk of the particle (positive electron affinity). We identify a charge-dependent increase of the extinction efficiency for low frequencies, a shift of the extinction resonance above the transverse optical phonon frequency, and a rapid variation of the polarization angles over this resonance. These effects could be used for non-invasive optical measurements of the charge of the particle.