ROTATIONAL ENERGY TRANSFERS IN IONIZED MOLECULAR GASES - THE NH4+ SYSTEM

The interaction between H+ ions and the ground electronic state of NH3 molecules is computed from first principles, using an expansion over analytic functions (GTO orbitals) to construct a potential energy surface (PES) at the SCF-HF level of approximation. By employing a rigid-rotor (RR) description of the symmetric-top target molecule, the interaction is expanded in symmetry-adapted coefficients, and the latter are fitted with analytic polynomials. The full quantum treatment of rotationally inelastic collisions at the energies of existing molecular beam experiments produces reasonable accord with these data and suggests physical reasons for the observed low efficiency of the inelastic processes.