Development of plasma-chemistry schemes: the call for a new paradigm

The development of "reaction mechanisms" for plasma chemistry, i.e., sets of reactions and corresponding rate coefficients that are validated against benchmark experiments, is mandatory to make sensible modelling predictions of low-temperature plasmas (LTP). This procedure must still be improved in the LTP community, where extensive validation of electron-impact cross sections by swarm analysis is well established, but the validation of plasma-chemistry models against benchmark experiments remains to some extent elusive. Indeed, although many modellers follow the procedure of comparing their results against experiment for many years, a community consensus on recommended practices and definition of experiments as golden standards to assess the results of the models is still missing [1]. In this work we report on a vast modelling work carried out at IST-Lisbon in collaboration with Laboratoire de Physique des Plasmas (LPP) in Paris that has led to the definition of reaction mechanisms e.g. for CO₂ [2], CO₂-O₂ [3], CO₂-N₂ [4] and CO₂-CH₄ plasmas. Further work involving IST, LPP and the Lomonosov Moscow State University (MSU) additionally led to a refined reaction mechanism for O₂ plasmas [5]. It is argued that the development of kinetic schemes for plasma chemistry should adopt a paradigm based on the comparison against standard validation tests. However, more experimental data from various independent researchers is necessary to evaluate possible problems of reproducibility or systematic errors, and to extend the conditions for validation.

[1] L. L. Alves et al, Plasma Sources Sci. Technol. 32 (2023) 023001

[2] T. Silva et al, J. CO2 Util. 53 (2021) 101719

[3] C. Fromentin et al, Plasma Sources Sci. Technol. 32 (2023) 024001

[4] C. Fromentin et al, Plasma Sources Sci. Technol. (in press: https://doi.org/10.1088/1361-6595/acce64)

[5] T. C. Dias et al, https://doi.org/10.48550/arXiv.2305.03674