On the fragmentation dynamics of NH3 → NH2 + H. I. MRD CI potential energy surfaces

To provide a potential energy surface (PES ) for a three-dimensional vibrational model of the dissociation dynamics of ammonia in the à state, accurate MRD-CI computations were carried out for a wide range of displacements in the out-of-plane and in-plane bending coordinates along the H(bond)NH₂ dissociation coordinate. Some characteristic features of the Ã-state PES , such as the height and position of the barrier to dissociation and the dependence of the PES on the out-of-plane angle, differ noticeably from earlier work on this system. The values for the height of the barrier computed from the MRD-CI extrapolation, full CI , and secular equation estimates are 0.38, 0.34, and 0.32 eV, respectively. © 1996 John Wiley & Sons, Inc.