Hybrid Quantum Model for Low-Energy Ion/Atom-Hydrogen Inelastic Collisions: Application to Na⁺+H^- and Na+H

A hybrid quantum model is introduced for low-energy ion/atom-hydrogen collisions. The model integrates ab initio calculations for low-lying states with asymptotic fitting for highly excited states, enabling fully quantum mechanical dynamics calculations that capture radial and rotational couplings across all internuclear distances, thereby addressing limitations of Landau–Zener models, which neglect short-range nonadiabatic interactions. Applied to the NaH system, the results for both mutual neutralization and excitation processes align well with fully quantum mechanical benchmarks for dominant channels. The analysis reveals the dominance of long-range ionic-covalent interactions for large cross sections and the significant influence of rotational coupling above 10 eV/u. Furthermore, discrepancies in weak excitation channels highlight the critical role of short-range non-adjacent couplings, which are often neglected in simplified models. This framework provides a robust tool for astrophysical non-local thermodynamic equilibrium modeling, thereby improving the accuracy of stellar abundance analyses.