Estimating inelastic heavy-particle - hydrogen collision data. II. Simplified model for ionic collisions and application to barium-hydrogen ionic collisions
Abstract
Aims: A simplified model is derived for estimating rate coefficients for inelastic processes in low-energy collisions of heavy particles with hydrogen, in particular, the rate coefficients with high and moderate values. Such processes are important for non-local thermodynamic equilibrium modeling of cool stellar atmospheres.
Methods: The derived method is based on the asymptotic approach for electronic structure calculations and the Landau-Zener model for nonadiabatic transition probability determination.
Results: It is found that the rate coefficients are expressed via statistical probabilities and reduced rate coefficients. It is shown that the reduced rate coefficients for neutralization and ion-pair formation processes depend on single electronic bound energies of an atomic particle, while the reduced rate coefficients for excitation and de-excitation processes depend on two electronic bound energies. The reduced rate coefficients are calculated and tabulated as functions of electronic bound energies. The derived model is applied to barium-hydrogen ionic collisions. For the first time, rate coefficients are evaluated for inelastic processes in Ba+ + H and Ba2+ + H- collisions for all transitions between the states from the ground and up to and including the ionic state.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- December 2017
- DOI:
- 10.1051/0004-6361/201731882
- Bibcode:
- 2017A&A...608A..33B
- Keywords:
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- atomic data;
- atomic processes;
- stars: atmospheres