Quantum photochemistry. Accurate quantum scattering calculations for an electronically nonadiabatic reaction

We present converged quantum mechanical scattering calculations of reaction and quenching probabilities for a problem involving an electronically excited product. The calculations correspond to two coupled potential energy surfaces representing the ground and first electronically excited state of H2Br. Results are presented for H + HBr → H2 + Br and H + Br → H2 + Br∗, where an asterisk denotes electronic excitation, and the lack of an asterisk denotes the electronic ground state. The calculations are carried out by linear algebraic variational methods with a multi-arrangement diabatic basis. These benchmark calculations are used to test a one-dimensional model, which is found to be quantitatively unreliable.