Semiclassical Trajectory Studies of Reactive and Nonreactive Scattering of OH(A2Σ+) by H2 Based on an Improved Full‐Dimensional Ab Initio Diabatic Potential Energy Matrix

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We present a new full‐dimensional diabatic potential energy matrix (DPEM) for electronically nonadiabatic collisions of OH(A 2Σ+) with H2, and we calculate the probabilities of electronically adiabatic inelastic collisions, nonreactive quenching, and reactive quenching to form H2O+H. The DPEM was fitted using a many‐body expansion with permutationally invariant polynomials in bond‐order functions to represent the many‐body part. The dynamics calculations were carried out with the fewest‐switches with time uncertainty and stochastic decoherence (FSTU/SD) semiclassical trajectory method. We present results both for head‐on collisions (impact parameter b equal to zero) and for a full range of impact parameters. The results are compared to experiment and to earlier FSTU/SD and quantum dynamics calculations with a previously published DPEM. The various theoretical results all agree that nonreactive quenching dominates reactive quenching, but there are quantitative differences between the two DPEMs and between the b=0 results and the all‐b results, especially for the probability of reactive quenching.