Accurate nonadiabatic dynamics.

This Perspective addresses the use of coupled diabatic potential energy surfaces (PESs) together with rigorous quantum dynamics in full or reduced dimensional coordinate spaces to obtain accurate solutions to problems in nonadiabatic dynamics. A recently developed technique for obtaining the requisite diabatic PESs is reviewed. Three examples are considered in detail, two, H2O and NH3 photodissociation, are treated in the full dimensionality while for the third, phenol photodissociation, a reduced dimensionality treatment is used. In all three examples, nonadiabatic dynamics is dominated by conical intersections, near which the Born-Oppenheimer approximation fails. The role of the conical intersection induced geometric phase in the adiabatic representation, as evinced by the molecular Aharonov-Bohm effect, is discussed.