New light shed on charge transfer in fundamental H+ + H2 collisions.

There is no consensus on the magnitude and shape of the charge transfer cross section in low-energy H+ + H2 collisions, in spite of the fundamental importance of these collisions. Experiments have thus been carried out in the energy range 15≤E≤5000  eV. The measurements invalidate previous recommended data for E≤200  eV and confirm the existence of a local maximum around 45 eV, which was predicted theoretically.

Ionization and electron capture in ion-molecule collisions: classical (CTMC) and semiclassical calculations.

Total cross-sections for electron capture and electron production in proton collisions with N2, CO and H2O, are evaluated using a classical trajectory Monte Carlo treatment for collision energies between 30 and 3000 keV. A semiclassical close-coupling treatment has been also employed for proton collisions with H2O, to discuss the accuracy of the CTMC treatment. Singly differential cross-sections for electron production have been also evaluated.

Influence of nuclear exchange on nonadiabatic electron processes in H(+)+H2 collisions.

H(+)+H(2) collisions are studied by means of a semiclassical approach that explicitly accounts for nuclear rearrangement channels in nonadiabatic electron processes. A set of classical trajectories is used to describe the nuclear motion, while the electronic degrees of freedom are treated quantum mechanically in terms of a three-state expansion of the collision wavefunction. We describe electron capture and vibrational excitation, which can also involve nuclear exchange and dissociation, in the E = 2-1000 eV impact energy range.

A study of conical intersections for the H3(+) system.

A parametrization of the three asymptotic conical intersections between the energies of the H3(+) ground state and the first excited singlet state is presented. The influence of an additional, fourth conical intersection between the first and second excited states at the equilateral geometry on the connection between the three conical regions is studied, for both diatomics-in-molecules and ab initio molecular data.

Study of ab initio molecular data for inelastic and reactive collisions involving the H3+ quasimolecule.

The lowest two ab initio potential energy surfaces (PES), and the corresponding nonadiabatic couplings between them, have been obtained for the H3+ system; the molecular data are compared to those calculated with the diatomic in molecules (DIM) method. The form of the couplings is discussed in terms of the topology of the molecular structure of the triatomic. The method of Baer is employed to generate "diabatic" states and the residual nonadiabatic couplings are calculated.