Quantum calculations of the rotational excitation of H₂ by proton impact at low energies

Ab initio quantum calculations are presented for the H⁺-H₂ system at several collision energies. The correct close-coupling (CC) equations are solved within the energy-corrected rigid-rotor (ECRR) approximation for the target molecule, and inelastic integral and differential cross sections between low rotational levels are thus obtained. The relevant adiabatic potential hypersurface given by self-consistent-field, configuration-interaction computed points was used here by expanding around the center of mass a general analytic expression recently suggested by Giese and Gentry. The energy dependence of the various transitions is examined and numerical convergence effects discussed. The nature of the molecular interaction with proton projectiles is discussed from the viewpoint of its direct bearing on the behavior of the various cross sections.