Microwave air plasmas in capillaries at low pressure II. Experimental investigation

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Section: O Atom Collisional-radiative Model In Co 2 Conversion Plasmamentioning

confidence: 99%

Resolving discharge parameters from atomic oxygen emission

Viegas

Vialetto

Steeg

et al. 2021

“…The species taken into account are O 2 (X) and O 3 (X) groundstate molecules, O 2 (a) and O 2 (b) electronically excited metastable states, O 3 (exc) vibrationally excited molecules, ground-state O( 3 P) and metastable O( 1 D) atoms, and O + 2 , O + and O − ions. The kinetic scheme was previously used to study inductive coupled plasmas [44], and very similar schemes were used to successfully describe microwave [45,46] and DC [47,48] discharges. The deterministic simulations are performed using the 0-D chemistry solver of the LisbOn Kinetics (LoKI) tool suite [49][50][51], for the same conditions and using the same kinetic scheme as in the KMC calculations.…”

Section: Validationmentioning

confidence: 99%

Kinetic Monte Carlo simulations of plasma-chemistry

Dias

Guerra

2020

This work presents a kinetic Monte Carlo algorithm to solve the gas-phase chemistry in low-temperature plasmas, as a first effort to achieve a unified formulation of the electron and heavy-particle kinetics based on Monte Carlo techniques. The implemented algorithm is successfully validated in the thermodynamic limit from the comparison with the traditional deterministic description using rate-balance equations. The accuracy of the Monte Carlo description of the rare species strongly depends on the number of particles used in the simulation. To surpass this limitation, two novel variance reduction techniques that significantly reduce the statistical fluctuations on the concentrations of the minor species are proposed and evaluated. These techniques lead to significant gains in computational time, up to factors of the order of 104 times in the cases studied, while ensuring the same quality of the solution.

“…The simulations presented in this study were carried out using the self-consistent LoKI numerical simulation tool, a global, volume averaged (0D) kinetic model introduced by Loureiro (1997, 1999) and successfully used for kinetic modelling of diverse plasma conditions (Kutasi et al 2010, Marinov et al 2013, Kutasi et al 2016, Stancu et al 2016. In this work the description of the oxygen kinetics is extended by including the calculation of the VDF of O 2 ground state molecules, which is detailed in section 3.2.…”

Section: Overview Of the Modelmentioning

confidence: 99%

Kinetics of highly vibrationally excited O₂(X) molecules in inductively-coupled oxygen plasmas

Annusova¹,

Marinov²,

Booth³

et al. 2018

The high degree of vibrational excitation of O 2 ground state molecules recently observed in inductively coupled plasma discharges is investigated experimentally in more detail and interpreted using a detailed self-consistent 0D global kinetic model for oxygen plasmas. Additional experimental results are presented and used to validate the model. The vibrational kinetics considers vibrational levels up to v=41 and accounts for electron impact excitation and de-excitation (e-V), vibration-to-translation relaxation (V-T) in collisions with O 2 molecules and O atoms, vibration-to-vibration energy exchanges (V-V), excitation of electronically excited states, dissociative electron attachment, and electron impact dissociation. Measurements were performed at pressures of 10-80 mTorr (1.33 and 10.67 Pa) and radio frequency (13.56 MHz) powers up to 500 W. The simulation results are compared with the absolute densities in each O 2 vibrational level obtained by high sensitivity absorption spectroscopy measurements of the Schumann-Runge bands for O 2 (X, v=4-18), O( 3 P) atom density measurements by two-photon absorption laser induced fluorescence (TALIF) calibrated against Xe, and laser photodetachment measurements of the O − negative ions. The highly excited O 2 (X, v) distribution exhibits a shape similar to a Treanor-Gordiets distribution, but its origin lies in electron impact e-V collisions and not in V-V up-pumping, in contrast to what happens in all other molecular gases known to date. The relaxation of vibrational quanta is mainly due to V-T energy-transfer collisions with O atoms and to electron impact dissociation of vibrationally excited molecules, e+O 2 (X, v)→O( 3 P)+O( 3 P).