title: Geometric Rotation of the Nuclear Gradient at a Conical Intersection: Extension to Complex Rotation of Diabatic States.
abstract: Nonadiabatic dynamics in the vicinity of conical intersections is of essential importance in photochemistry. It is well known that if the branching space is represented in polar coordinates, then for a geometry represented by angle θ, the corresponding adiabatic states are obtained from the diabatic states with the mixing angle θ/2. In an equivalent way, one can study the relation between the real rotation of diabatic states and the resulting nuclear gradient. In this work, we extend the concept to allow a complex rotation of diabatic states to form a nonstationary superposition of electronic states. Our main result is that this leads to an elliptical transformation of the effective potential energy surfaces; i.e., the magnitude of the initial nuclear gradient changes as well as its direction. We fully explore gradient changes that result from varying both θ and ϕ (the complex rotation angle) as a way of electronically controlling nuclear motion, through Ehrenfest dynamics simulations for benzene cation.
authors.affiliation: Computational Chemistry Group, Institute of Theoretical Chemistry, University of Stuttgart , Pfaffenwaldring 55, 70569 Stuttgart, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Meisner
authors.affiliation: Department of Chemistry, Imperial College London , London SW7 2AZ, United Kingdom.
authors.forename: Morgane
authors.initials: M
authors.lastname: Vacher
authors.affiliation: Department of Chemistry, Imperial College London , London SW7 2AZ, United Kingdom.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Bearpark
authors.affiliation: Department of Chemistry, Imperial College London , London SW7 2AZ, United Kingdom.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Robb