Nonadiabatic ionic–covalent transitions. Exponential-linear model for the charge exchange and neutralization reactions Na+H ⇄ Na++H−

A previous study of charge exchange processes taking place through ionic–covalent transitions is extended to the case of Na+H and Na++H− collisions. A five-state molecular expansion, with the inclusion of two-electron translation factors, is employed to calculate the charge exchange and neutralization cross sections. Transitions at the first two pseudocrossings between the energy curves, practically determine the cross sections in the energy range 0.16–5 keV amu−1. We also show that the widely used multichannel Landau–Zener theory is totally inadequate, to treat these transitions.