Model approach for low-energy inelastic atomic collisions and application to Al+H and Al++H−

Abstract

A model approach is derived for estimates of cross sections and rate coefficients in low-energy inelastic collisions of hydrogen atoms and negative ions with other atoms and positive ions, which are of astrophysical interests. The approach is based on the asymptotic method for electronic molecular structure determination and on the branching probability current method for a nonadiabatic nuclear dynamical treatment. The derived approach is applied to low-energy Al + H and Al${}^{+}$ + H${}^{\ensuremath{-}}$ inelastic collisions. It is shown that the processes with the largest values of cross sections and rates are the excitation and de-excitation ones between the Al($3d$) and Al($4p$) states in collisions with H, as well as the ion-pair formation and the mutual neutralization processes between these states and the ionic state; the second largest cross sections correspond to the similar processes involving the Al($4s$) state. The mechanisms of the processes are discussed in detail.