Role of vibrational energy relaxation in the photoinduced nonadiabatic dynamics of pyrrole at the 1πσ*-S0 conical intersection

The influence of intramolecular vibrational relaxation on the nonadiabatic dynamics at the (1)A(2)(pi sigma*)-S-0 conical intersection of pyrrole has been investigated within the reduced-density-matrix formalism. The system Hamiltonian represents the (1)A(2)(pi sigma*)-S-0 conical intersection of pyrrole, taking the dominant tuning and coupling modes into account. Within the system-plus-bath model, the system is assumed to couple with a harmonic bath, which represents the many other photoinactive vibrational modes. The system-bath coupling results in vibrational energy transfer from the system to the bath. An extension of Redfield theory has been developed, which is suitable for the description of quantum dissipative dynamics of a dissociative system. The electronic population probabilities, the dissociation probability, the internal-conversion probability and their dependence on the system-bath coupling strength have been explored by the calculations. It is shown that the system-bath coupling reduces the dissociation probability and enhances the internal-conversion probability. (C) 2008 Elsevier B.V. All rights reserved.