Reduced Molecular Plasma Kinetics with Non-Boltzmann Vibrational Distribution
Abstract
Vibrational kinetics can strongly affect energy transfer, chemical kinetics, and discharge behavior in molecular plasmas, but resolving all internal states is often impractical for reactor-scale simulation. Compact, physics-based vibrational closures are particularly needed when complete state-to-state (StS) data are limited. Starting from a detailed H2 StS plasma-kinetics framework coupled to an electron-Boltzmann calculation, this work develops a reduced vibrational-kinetics formulation. The H2 vibrational ladder is reduced to two non-Boltzmann groups that evolve their population and internal energy. State-resolved reaction rates and associated energy-exchange terms are projected onto the groups for subsequent tabulation in reactor-scale plasma models. StS-informed samples of the reduced-model are propagated for pulsed RF H2 plasmas across a scan of pulse-averaged absorbed power and compared with the corresponding StS simulations. Predictions from the sampled models reproduce the bulk plasma response, including electron density, atomic-H density, and H3+ density. Discrepancies in H- production and the upper-energy-group vibrational temperature persist across the sampled reductions. This indicates a limitation of the present VDF reconstruction rather than the nominal parameter choice. Tail-sensitive processes therefore require a more accurate representation of the vibrational distribution.
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BibTeX
@misc{pokharel2026reduced,
title = {{Reduced Molecular Plasma Kinetics with Non-Boltzmann Vibrational Distribution}},
author = {Sagar Pokharel and Laxminarayan L. Raja},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.25738},
eprint = {2610.25738},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.25738},
}
RIS
TY - UNPB
TI - Reduced Molecular Plasma Kinetics with Non-Boltzmann Vibrational Distribution
AU - Sagar Pokharel
AU - Laxminarayan L. Raja
PY - 2026
DA - 2026/10/19
PB - arXiv
DO - 10.48550/arxiv.2610.25738
UR - https://arxiv.org/abs/2610.25738
AB - Vibrational kinetics can strongly affect energy transfer, chemical kinetics, and discharge behavior in molecular plasmas, but resolving all internal states is often impractical for reactor-scale simulation. Compact, physics-based vibrational closures are particularly needed when complete state-to-state (StS) data are limited. Starting from a detailed H_2 StS plasma-kinetics framework coupled to an electron-Boltzmann calculation, this work develops a reduced vibrational-kinetics formulation. The H_2 vibrational ladder is reduced to two non-Boltzmann groups that evolve their population and internal energy. State-resolved reaction rates and associated energy-exchange terms are projected onto the groups for subsequent tabulation in reactor-scale plasma models. StS-informed samples of the reduced-model are propagated for pulsed RF H_2 plasmas across a scan of pulse-averaged absorbed power and compared with the corresponding StS simulations. Predictions from the sampled models reproduce the bulk plasma response, including electron density, atomic-H density, and H_3^+ density. Discrepancies in H^- production and the upper-energy-group vibrational temperature persist across the sampled reductions. This indicates a limitation of the present VDF reconstruction rather than the nominal parameter choice. Tail-sensitive processes therefore require a more accurate representation of the vibrational distribution.
ER -