Quasiclassical trajectory study of the postquenching dynamics of OH A 2Σ+ by H2/D2 on a global potential energy surface

We report full-dimensional, electronically adiabatic potential energy surfaces (PESs) for the ground state (1A') and excited state (2A') of OH3. The PESs are permutationally invariant fits to roughly 23 000 electronic energies (MRCI+Q/aVTZ). Classical trajectory calculations of the postquenching dynamics of OH A (2)Sigma(+) are carried out on the 1A' PES for H-2 and D-2, at previously identified conical intersections (CoIs) [B. C. Hoffman and D. R. Yarkony, J. Chem. Phys. 113, 10091 (2000)]. The initial momenta are sampled fully and partially microcanonically, corresponding to adiabatic and diabatic models of the dynamics, respectively. Branching ratios of reactive to nonreactive channels from separate C-2v, C-infinity v, and C-s symmetries of CoIs are calculated, as are final rovibrational state distributions of OH and H-2 products. The rovibrational distributions of the OH and D-2 products, the D/H-atom translational energy distribution are calculated and compared to experimental ones. Agreement for these observable quantities is good. The branching between reactive and nonreactive quenching is sensitive to the momenta sampling; very good agreement with experiment is obtained using the diabatic sampling but not with the adiabatic sampling. The vibrational state distributions of H2O and HOD (although not measured by experiment) are also presented. (C) 2010 American Institute of Physics. [doi:10.1063/1.3488167]