Quenching rate constants for reactions of Ar(4p′[1/2]0, 4p[1/2]0, 4p[3/2]2, and 4p[5/2]2) atoms with 22 reagent gases

State-resolved modeling of electronic excitation in weakly ionized oxygen mixtures

Electronic excitation and ionization in oxygen-argon mixtures are analyzed using a three-temperature electronic state-resolved model and evaluated using recent experimental data from reflected shock experiments. A detailed description of the model formulation and parameter selection is provided. Excellent agreement is obtained between model predictions and experimental measurements of O_{2} number density during dissociation in mixtures of 2%-5% O_{2} dilute in argon. Next, electron number density measurements are leveraged to infer a rate constant for the heavy particle impact excitation of argon, facilitating improved modeling of net ionization and a clearer understanding of the electronic excitation kinetics of oxygen. The electronic state-resolved model is then assessed using measured data for three electronic states of atomic oxygen. The model successfully reproduces the multistage behavior observed in the measured time histories and yields new insights into the multistage behavior that revises previous interpretations. For several experiments, the modeling choices involved in the calculation of escape factors significantly influence the predicted time histories. A global sensitivity analysis considering nearly 300 parameters is then conducted to identify which model parameters most sensitively influence the predicted excited state populations. Excitation of the measured states from the metastable levels and collisional excitation between the three measured states are important across all conditions. The excited state populations demonstrate complex sensitivities involving a large number of collisional and radiative processes, highlighting the importance of adopting a detailed modeling approach when interpreting excited state measurements.

Disrupting the spatio-temporal symmetry of the electron dynamics in atmospheric pressure plasmas by voltage waveform tailoring

Single frequency, geometrically symmetric Radio-Frequency (rf) driven atmospheric pressure plasmas exhibit temporally and spatially symmetric patterns of electron heating, and consequently, charged particle densities and fluxes. Using a combination of phase-resolved optical emission spectroscopy and kinetic plasma simulations, we demonstrate that tailored voltage waveforms consisting of multiple rf harmonics induce targeted disruption of these symmetries. This confines the electron heating to small regions of time and space and enables the electron energy distribution function to be tailored.

Role of excited atoms in decaying low-pressure argon plasma

The influence of the kinetics of excited atoms on the characteristics of an inductively coupled plasma in argon during the early afterglow is studied. A self-consistent model including the nonlocal approach for the kinetic treatment of the electrons is applied. Parameters of both the steady state of the rf discharge and the decay phase are presented. Results for the steady-state densities of excited atoms as well as temporal evolutions of the wall potential and mean energy of electrons are discussed in comparison with experimental data available from the literature. The ionization kinetics of the electrons, the electron power balance, and the main kinetic pathways for excited argon atoms are analyzed in the pressure range between 0.5 and 133 Pa . In particular, a significant influence of the excited atoms on the plasma behavior in steady state and during the afterglow is found.