Coupling of Plasma Chemistry, Vibrational Kinetics, Collisional‐Radiative Models and Electron Energy Distribution Function Under Non‐Equilibrium Conditions

Abstract

The coupling between the electron energy distribution function (eedf) and the kinetics of vibrationally and electronically excited states is discussed. The first case study concerns the role of heterogeneous recombination in affecting the concentration of atomic hydrogen in RF plasmas, with consequences on eedf and negative ion formation. The coupling of eedf and a collisional‐radiative model for atomic hydrogen is discussed for optically thin and thick plasmas, finding large differences in the creation of eedf plateaux. The last case study deals with a self‐consistent coupling of eedf and kinetics of vibrationally and electronically excited states in CO2 cold plasmas emphasizing the role of pure vibrational mechanisms in the dissociation of CO2.

On the plasma confinement by acoustic resonance

“…In contrast, we could not make any conclusive measurement when the plasma was not in the spherical resonance. So it appears that, in this case, the electron impact dissociation mechanisms have a determinant effect, in contrast to the opposite case, where it is the pure vibrational mechanisms that are governing dissociation, like in the case study [20].…”

“…The dissociation rate from the pure vibrational mechanisms, in which only heavy particle collisions are involved, may become competitive with the direct electron impact dissociation mechanisms, as in the case study of Pietanza et al on a CO 2 microwave plasma, based on a model of the coupling of the electron energy distribution with the vibrational kinetics [19]. The afterglow decay might be very fast, as long as the electron temperature lays above the vibrational temperature, as it has been found by Capitelli et al, also in numerical modelizations of a CO 2 plasma [20]. In a model of the triangular response to short microwave pulses, the decay is composed of two successive exponential parts:…”

“…Modeling the excited state kinetics is necessary to describe fully the complex phenomena that occur in the bulb. Such a task is out of scope in the present study, but we hope that it will be achieved in the future, as nowadays the distribution functions of the electron energy, as well as the vibration and electronic states, can be calculated by numerical simulation taking into account optical thickness and plasma geometry [20]. Deeper understanding of the interplay between the plasma chemistry and the acoustics, as required in our analysis of the plasma ball formation, might lead to futher discoveries in plasma sonochemistry.…”

“…As seen in Sect. 4.4, the frozen velocity of sound is a growing function of temperature, see (20). Moreover, the mean molar mass (M ) decreases when α increases, see (5), adding to the acceleration of the wave.…”

Special Issue on Numerical Modelling of Low‐Temperature Plasmas for Various Applications – Part I: Review and Tutorial Papers on Numerical Modelling Approaches

“…Furthermore, the authors also explain how to bridge the gap between global models and fluid models by discussing methods of extending global modelling techniques to include variations in either time or space. Capitelli and colleagues, from PLASMI Lab in Bari and Université Paris 13, present the coupling of plasma chemistry, vibrational kinetics, collisional‐radiative models and the electron energy distribution function at non‐equilibrium conditions, for two case studies, i.e., atomic hydrogen and CO 2 . Finally, as the kinetic and continuum approaches both have their advantages and limitations, a third option exists in combining these methods into a hybrid approach.…”