Strong Correlation Effects in Atmospheric Pressure Plasmas

Abstract

In order to understand how strong correlation effects influence transport in atmospheric pressure plasmas it is necessary to study how the presence of neutral atoms affect the interactions between charged particles and vice versa. In this work, a partially ionized atmospheric pressure plasma was studied using the open source molecular dynamics simulator LAMMPS. Short (neutral-neutral), medium (charge-neutral) and long (charge-charge) range interactions were included while considering the electrons as a background non-interacting species. Diffusion coefficients and radial distribution functions were computed in order to study the transport properties of the plasma and the correlation of the different interactions involved. Strong ion-ion correlations were observed as predicted from the theory of strongly coupled plasmas. While at room temperature neither the neutral-neutral nor the ion-neutral interaction are expected to be strongly coupled, we observed signatures of strong ion-neutral and neutral-neutral correlations during the evolution of the discharge. We suggest that this behavior is due to the interaction with ions, which are strongly coupled at room temperature and atmospheric pressure. These findings suggest that atmospheric pressure plasmas are sufficiently dense that they are influenced by strong correlation effects associated with many-body interactions that are not treated in the dilute limit.