Ab initio dynamics of the He+H2+→HeH++H reaction:: a new potential energy surface and quantum mechanical cross-sections

The reaction He + H-2(+) (nu, j = 0) --> HeH+(nu' = 0, j') for nu = 0, 1, 2 and 3 and for scattering energies near the threshold (0. 95-1.15 eV) has been studied by calculating ab initio points at MRCI level and 'exact' integral quantum reactive cross-sections. More than 1400 nuclear geometries have been chosen to cover the most important regions for the dynamics, an extended set of points being taken directly on a hyperspherical coordinate grid. A many-body expansion with a large number of terms permits an accurate analytical representation of the potential energy surface with a root-mean-square deviation <12 meV. The hyperquantization algorithm has been extended to obtain quantum mechanical integral cross-sections which are compared with previous calculations and with experimental results.