Collective modes in free plasmas subjected to a radiation field

TL;DR

This paper investigates how an external electromagnetic field influences the collective oscillations in unmagnetized plasmas, revealing smoother damping, exponential decay of plasmon frequencies, and significant effects from single photon processes.

Contribution

It provides new insights into plasma behavior under classical electromagnetic fields, especially regarding damping and frequency modulation, extending previous research findings.

Findings

Collective modes are damped more smoothly and over a smaller frequency range.

Plasmon frequencies decay exponentially with increasing external field amplitude.

Single photon processes significantly reduce the modulation frequency range.

Abstract

In this study we report the effects of an external electromagnetic field on the collective properties of unmagnetized plasmas. The calculations are carried out in the semi-classical approximation, i.e., the electromagnetic field is treated classically and the electrons from a quantum mechanical viewpoint. The results show that the collective modes are damped away more smoothly and in a smaller frequency range than those reported by previous studies. An exponential-like decay of the plasmon frequencies as a function of the external field amplitude is readily observed. We successfully recreate the results of previous studies. We also find that the single photon processes has a pronounced effect on the decrease of the frequency range of modulation.