Inelastic Processes in Low-energy Sulfur–Hydrogen Collisions

Abstract

Abstract The cross sections and rate coefficients for inelastic processes in low-energy collisions of sulfur atoms and positive ions with hydrogen atoms and negative ions are calculated for the collisional energy range and for the temperature range 1000–10,000 K. Fifty-five covalent states and two ionic ones are considered. The ground ionic state provides only molecular symmetry, while the first-excited ionic state provides three molecular symmetries: , , and . The study of sulfur–hydrogen collisions is performed by the quantum model methods within the Born–Oppenheimer formalism. The electronic structure of the collisional quasimolecule is calculated by the semiempirical asymptotic method for each considered molecular symmetry. For nuclear dynamic calculations, the multichannel formula in combination with the Landau–Zener model is used. Nuclear dynamics within each considered symmetry is treated separately, and the total rate coefficients for each inelastic process have been summed over all symmetries. The largest values of the rate coefficients (exceeding ) correspond to the mutual neutralization processes in (the ground ionic state being the initial state), as well as in (the first-excited ionic state being the initial state) collisions. At the temperature 6000 K, the rate coefficients with large magnitudes have the values from the ranges and , respectively. The calculated rate coefficients with large and moderate values are important for NLTE stellar atmosphere modeling.