On the energy dependence of inelastic cross sections

The new accurate two-state quantum calculations of the inelastic cross sections in H + Li, Na collisions for energies from the thresholds and till 100 eV or 600 eV are performed, and the results are compared with the Landau-Zener model cross sections in both the diabatic and the adiabatic representations. It is found that the low-energy inelastic cross section is very sensitive to nonadiabatic coupling and, hence, the new NaH coupling is computed. The numerical solutions of the coupled channel equations are checked by independent calculations indicating that the quantum results are accurate. These checks are done by means of the analytic formula for a nonadiabatic transition probability derived within the perturbation approach. Both the Landau-Zener-like and the non-Landau-Zener-like behaviour of the excitation cross sections are found.