Volume 625, May 2019
|Number of page(s)||11|
|Section||Atomic, molecular, and nuclear data|
|Published online||17 May 2019|
Excitation and charge transfer in low-energy hydrogen atom collisions with neutral carbon and nitrogen⋆
Max Planck Institute für Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
2 Theoretical Astrophysics, Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden
Accepted: 30 March 2019
Low-energy inelastic collisions with neutral hydrogen atoms are important processes in stellar atmospheres, and a persistent source of uncertainty in non-LTE modelling of stellar spectra. We have calculated and studied excitation and charge transfer of C I and of N I due to such collisions. We used a previously presented method that is based on an asymptotic two-electron linear combination of atomic orbitals (LCAO) model of ionic-covalent interactions for the adiabatic potential energies, combined with the multichannel Landau-Zener model for the collision dynamics. We find that charge transfer processes typically lead to much larger rate coefficients than excitation processes do, consistent with studies of other atomic species. Two-electron processes were considered and lead to non-zero rate coefficients that can potentially impact statistical equilibrium calculations. However, they were included in the model in an approximate way, via an estimate for the two-electron coupling that was presented earlier in the literature: the validity of these data should be checked in a future work.
Key words: atomic data / atomic processes / line: formation / radiative transfer / stars: abundances
Atomic data are available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (220.127.116.11) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/625/A78 and at https://github.com/barklem/public-data
© A. M. Amarsi and P. S. Barklem 2019
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Open Access funding provided by Max Planck Society.
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