Electron collision cross sections for H₂ and NH₃ relevant to N₂-H₂ plasma modelling

This contribution uses swarm analysis to propose complete and consistent electron-impact cross section sets [1] for ground-state H₂ and NH₃ for the efficient modelling of N₂-H₂ plasmas. For H₂, we update the cross section set published in the IST-Lisbon database of LXCat [2], while for ammonia we propose a novel set of direct cross sections. The swarm analysis was carried out using the LisbOn KInetics Boltzmann solver (LoKI-B) [3-4], to calculate electron transport parameters as well as several reduced Townsend coefficients from different cross-section sets [5-8]. Results were compared with the corresponding available measurements [9], and some cross sections were adjusted to improve the swarm predictions. In this case, the most relevant updates are with the cross sections for the excitation to H₂(B¹Σᵤ + ) and H₂(C¹Πᵤ) states, the dissociative excitation of H₂(b³Σᵤ+) state, and the dissociative ionization yielding H(1s) + H+ . For NH₃, the new cross section set was built from the Hayashi dataset on LXCat [8], which was updated with cross sections recommended by Snoeckx et al. [7]. When used in a two-term electron Boltzmann solver, the cross-sections predict swarm parameters in agreement with experimental measurements, within less than 15%.



References

[1] Zhang, B. et al., J. Phys. D. Appl. Phys. 56, 134001 (2023)

[2] The IST-Lisbon database on LXCat www.lxcat.net/IST-Lisbon

[3] Tejero-Del-Caz, A. et al., Plasma Sources Sci. Technol. 28 043001 (2019)

[4] https://github.com/IST-Lisbon/LoKI

[5] Celiberto, R. et al., reference At. Data Nucl. Data Tables. 77 161 (2001)

[6] Zammit, M. et al., Phys.Rev.A. 95, 022708 (2017)

[7] Snoeckx, R. et al., Plasma Sources Sci. Technol. 32 115020 (2023)

[8] Hayashi database on LXCat www.lxcat.net/Hayashi

[9] Dutton, A. J. Phys. Chem. Ref. Data 4 3 (1975)