Ultrafast excited-state charge transfer at a conical intersection: effects of an environment

Excited-state processes at conical intersections (CIs) involving charge transfer phenomena can depend sensitively on the influence of a polar and polarizable environment. To describe the chromophore-environment interaction for such situations, we propose a theoretical formulation in terms of a diabatic free energy model depending on molecular coordinates plus a solvent coordinate. We focus on the S1-S0 CI in protonated Schiff bases, representing a model for retinal isomerization, and comment upon static and dynamic solvation effects.