Data on inelastic processes in low-energy collisions of barium atoms and ions with hydrogen atoms and anions

Abstract

ABSTRACT Inelastic rate coefficients for 686 partial processes in low-energy Ba + H, Ba+ + H−, Ba++ H and Ba2+ + H− collisions are calculated. These data are needed for the non-local thermodynamic equilibrium (non-LTE) modelling of Ba i and Ba ii spectra, especially in cool stellar atmospheres. The calculations of the rate coefficients are performed by means of the quantum model approach, based on the asymptotic semi-empirical method for the electronic structure calculations and on multichannel formulas for the non-adiabatic nuclear dynamical calculations. The inelastic rate coefficients for all transitions between the 17 lowest covalent states and one ionic molecular state in Ba + H and Ba+ + H− collisions, as well as the inelastic rate coefficients for all transitions between the 19 lowest covalent states and one ionic molecular state in Ba+ + H and Ba2+ + H− collisions are calculated. In Ba+ + H− collisions, the highest rate coefficients correspond to the mutual neutralization processes into the Ba(6s6p1P°), Ba(6s7s3S) and Ba(6s7s1S) final states, with the largest value of 5.93 × 10−8 cm3 s−1 at T = 6000 K for the process Ba+ + H− → Ba(6s7s3S) + H. The highest rate coefficient for excitation and de-excitation processes in Ba + H collisions corresponds to the Ba(6s7s1S) → Ba(6s7s3S) transition, with the value of 7.62 × 10−9 cm3 s−1 at T = 6000 K. In Ba2+ + H− collisions, the highest rate coefficients correspond to the neutralization processes into the Ba+( 7p2P°), Ba+( 4f 2F°), Ba+( 6d 2D) and Ba+( 7s 2S) final states. The highest neutralization rate has the value of 3.96 × 10−8 cm3 s−1 at T = 6000 K for the Ba2+ + H− → Ba+( 7p 2P°) + H process. The largest rate coefficient for excitation and de-excitation processes in Ba+ + H collisions corresponds to the Ba+(7s 2S) → Ba+( 6p 2P°) transition, with the value of 1.23 × 10−9 cm3 s−1 at T = 6000 K.