CHARGE-TRANSFER DYNAMICS IN PHOTOPHYSICAL SYSTEMS - A CASE OF SADDLE-POINT AVOIDANCE

The simple bidimensional model of a reactive coordinate coupled to a h armonic mode is known to display varied dynamical behaviour, due to th e interplay of energetic and frictional factors. Molecular systems whi ch exhibit the photophysical process of intramolecular charge transfer generally are characterized by an internal coordinate coupled to the solvent polarization. They therefore provide an appealing application of the dynamic model, by identifying a solute variable with an intrins ic timescale tau(R), and a macroscopic solvent variable with relaxatio n time tau(S). In this paper, a theoretical analysis based on a bidime nsional diffusion equation suggests that time-dependent Stokes shifts observed in system undergoing intramolecular charge transfer processes may provide evidence of a kinetic pathway which implies saddle point avoidance.