Estimating inelastic heavy-particle–hydrogen collision data

I. Simplified model and application to potassium-hydrogen collisions^⋆

¹ Max-Planck Institute for Astrophysics, Postfach 1371, 85741 Garching, Germany
e-mail: andrey.k.belyaev@gmail.com
² Department of Theoretical Physics and Astronomy, Herzen University, 191186 St. Petersburg, Russia

Received: 21 April 2017
Accepted: 4 July 2017

Abstract

Aims. We derive a simplified model for estimating atomic data on inelastic processes in low-energy collisions of heavy-particles with hydrogen, in particular for the inelastic processes with high and moderate rate coefficients. It is known that these processes are important for non-LTE modeling of cool stellar atmospheres.

Methods. Rate coefficients are evaluated using a derived method, which is a simplified version of a recently proposed approach based on the asymptotic method for electronic structure calculations and the Landau-Zener model for nonadiabatic transition probability determination.

Results. The rate coefficients are found to be expressed via statistical probabilities and reduced rate coefficients. It turns out that the reduced rate coefficients for mutual neutralization and ion-pair formation processes depend on single electronic bound energies of an atom, 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 potassium-hydrogen collisions. For the first time, rate coefficients are evaluated for inelastic processes in K+H and K⁺+H⁻ collisions for all transitions from ground states up to and including ionic states.