Spin-orbit corrected full-dimensional potential energy surfaces for the two lowest-lying electronic states of FH2O and dynamics for the F + H2O → HF plus OH reaction

The lowest two electronic states of FH2O both correlate adiabatically to the F(P-2) + H2O and HF + OH(X-2 Pi) asymptotes, thus facilitating the title reaction. To understand the reaction dynamics, global potential energy surfaces (PESs) for the two electronic states are constructed based on more than 30 000 points at the Davidson corrected multi-state multi-reference configuration interaction level. Spin-orbit corrections at the complete active space self-consistent field level are included in both PESs. The spin-orbit corrected ground state PES retains a relatively deep pre-reaction van der Waals well and a reactant-like transition state with a classical barrier of 4.2 kcal/mol. The spin-orbit corrected excited state PES has, on the other hand, a very shallow pre-reaction van derWaals complex and a much higher (17.6 kcal/mol) classical barrier, also featuring a reactant-like transition state. The adiabatic F + H2O -> HF + OH reaction dynamics on these two PESs are investigated using both quasi-classical trajectory and full-dimensional wave packet methods. Both reaction pathways produce internally excited HF and relatively cold OH, consistent with a direct abstraction mechanism. In addition, the spin-orbit corrections on the ground electronic state have a limited impact on the dynamics. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4791640]