J. Chem. Theory Comput. 2019, 15, 7, 3929-3940

A full-dimensional simulation of the photo-dissociation of 1,3-cyclohexadiene in the manifold of three electronic states was performed via non-adiabatic surface hopping dynamics using extended multi-state complete active space second-order perturbation (XMS-CASPT2) electronic structure theory with fully analytic non-adiabatic couplings. With the 47±8% product quantum yield calculated from the 136 trajectories, generally 400 fs-long, and an estimated excited lifetime of 89±9 fs, our calculations provide a detailed description of the non-adiabatic deactivation mechanism, showing the existence of an extended conical intersection seam along the reaction coordinate. The nature of the preferred reaction pathways on the ground state is discussed and extensive comparison to the previously published full dimensional dynamics calculations is provided.