Revisiting the potential energy surface for the reaction at the full configuration interaction level

A new potential energy surface is proposed for the title reaction. Calculations have been carried out using the full configuration interaction method and an extended basis set. The selection of geometries is based on an earlier paper [P. Palmieri et al., Mol. Phys. 98 (2000) 1835], where calculations had been made at MRCI level including all single and double excitations from the CASSCF space. Care was taken in blending the long-range two-body interactions with the short-range three-body contributions, specifically described in a hyperspherical reference frame. A many-body expansion fit is presented, with root-mean-square deviation 6 meV, adequate for further investigations of the dynamics.