Microscopic theory of vibronic dynamics in linear polyenes

We propose an approach to calculate dynamical processes at an ultrafast time scale in molecules in which vibrational and electronic motions are strongly mixed. The relevant electronic orbitals and their interactions are described by a Hubbard model, while electron-phonon interaction terms account for the dependence of the hopping on bond length and the dependence of the equilibrium bond length (atomic radii) on the local charge. The latter term plays a crucial role in the nonadiabatic internal-conversion process of the molecule. The time-resolved photoelectron spectra are in good qualitative agreement with experiments.