The barrier topography of the H + F2 potential energy surface
Abstract
The potential energy surfaces (PESs) for the electronic ground state and the three lowest excited states of the H + F2
reaction have been studied by ab initio multireference singles and doubles configuration interaction (MRCI-SD) calculations. Our main focus is laid on the description of the angular dependence of the barrier region on the ground state surface. In general, except for the cases of increased symmetry, the barrier arises from avoided-crossing interactions of the two lowest 2A′ states. In the collinear case it is the interaction between the two lowest Σ states which is responsible for the barrier. Due to the weak interaction of these
well-separated and not even neighboring states the barrier is relatively low. For