Topographical features of potential energy surfaces of the B+O-2 chemical reaction

Reactivities of spin-orbit states in B(P-2(1/2), (3/2)) + O-2(X (3) Sigma(g)(-)) --> BO(X (2) Sigma(+), A (2) Pi) + O(P-3(J)) have been studied by fluorescence imaging techniques. From experimentally measured reactivities of the P-2(1/2) and P-2(3/2) spin-orbit states of B atoms toward O-2 molecules and model calculations, an avoided intersection of potential energy surfaces in the entrance valley can be deduced. From the A --> X chemiluminescent spectra of BO* products under crossed beam conditions, the spatial patterns of BO* chemiluminescences, and fluorescence imagings of ground state BO radicals, it was inferred that both vibrationally excited BO(X (2) Sigma(+)) and electronically excited BO(A (2) Pi) products are formed in the B + O-2 reaction. The reaction channel that leads to the formation of A state BO* correlates solely with B atoms in the P-2(3/2) spin-orbit state. On the other hand, half of the population of this P-2(3/2) level can cross efficiently to a ground state reaction channel, in which the formation of X state BO correlates adiabatically with B atoms in the P-2(1/2) spin-orbit state. The excited state reaction channel exhibits a small potential barrier, while the ground state reaction channel has an attractive potential energy surface so that the energy release is channeled predominantly into the vibrational mode of BO. Consequently, the avoided intersection of potential energy surfaces and a barrierless, attractive lower sheet are the major topographical features of the B + O-2 reaction.