Improved potential energy surfaces for the reaction O(3<i>P</i>)+H2→OH+H

We present global 3A′ and 3A″ potential energy surfaces for the reaction O(3P)+H2→OH+H and its isotopic analogs. The new surfaces are based in part on the surface of Lee et al. [J. Chem. Phys. 76, 3563 (1982)] for collinear O–H–H, which is modified to give accurate properties for reactants and products. The potentials for noncollinear O–H–H geometries are based on bending energies of Bowman et al. [J. Chem. Phys. 81, 1739 (1984)] as fit previously and called surface set M2 by two of the authors [B. C. Garrett and D. G. Truhlar, Int. J. Quantum Chem. 29, 1463 (1986)], and the potentials for H–O–H geometries are based on a new interpolation scheme. The new surfaces treat the approach of an O to either end of H2 equivalently. We used improved canonical variational transition state theory calculations with the least-action ground-state tunneling approximation (ICVT/LAG) to recalibrate the classical barrier height to 13.0 kcal/mol. The ICVT/LAG rate constants calculated using the new surfaces are in excellent agreement with experimental values over the temperature range 298–2400 K. Rate constants and kinetic isotope effects for reactions involving D2 and HD also are presented and analyzed. Here again, the theoretical results are in very good agreement with experiments.