AB-INITIO STUDY OF THE SPECTROSCOPY, KINETICS, AND THERMOCHEMISTRY OFTHE BN2 MOLECULE

Several low-lying structures and electronic states of the BN2 molecule have been studied using complete active space SCF, multireference ave raged coupled-pair functional (ACPF), and coupled-cluster (CCSD(T)) me thods. BNN(2PI) and BN2(2A1) are very close together in energy: at the ACPF level, the separation is 2.8 kcal/mol. The potential surface for the transition between these structures appears to have a significant energy barrier, so it is surprising that the 2A1 state has not yet be en observed. Conversely, the low-lying BN2(2B2) state has a very low b arrier towards dissociation, which explains why it has not been observ ed. The symmetric linear species NBN(2PI), on the other hand, is subst antially higher in energy, but has a very large barrier towards dissoc iation and is therefore observed experimentally. At our highest level of theory, the ground BNN(2PI) state is nearly isoenergetic with B(2P) +N2(X 1SIGMA+).