Crossed molecular beams and quasiclassical trajectory studies of the reaction O(1D)+H2(D2)

The dynamics of the reactions O(D-1) + H-2 --> OH + H and O(D-1) + D-2 --> OD + D have been investigated in crossed molecular beam experiments with mass spectrometric detection at the collision energies of 1.9 and 3.0 kcal/mol, and 5.3 kcal/mol, respectively. From OH(OD) product laboratory angular and velocity distribution measurements, center-of-mass product translational energy and angular distributions were derived. The angular distributions are nearly backward-forward symmetric with a favored backward peaking which increases with collision energy. About 30% of the total available energy is found to be channeled into product translational energy. The results are compared with quasiclassical trajectory calculations on a DIM (diatomic-in-molecules) potential energy surface. Related experimental and theoretical works are noted. Insertion via the 1 (1)A' ground state potential energy surface is the predominant mechanism, but the role of a second competitive abstraction micromechanism which should evolve on one of (or both) the first two excited surfaces (1)A" and 2 (1)A' is called into play at all the investigated energies to account for the discrepancy between theoretical predictions and experimental results. (C) 1998 American Institute of Physics.