Vibronic coupling model to calculate the photoelectron spectrum of phenol

The photoelectron spectrum for the two lowest ionisation bands of phenol has been simulated using quantum dynamic methods. A vibronic coupling Hamiltonian was set up consisting of seven vibrational modes and the first two ionised states. Parameters for the model are obtained by fitting adiabatic surfaces to a series of points calculated using ab initio methods. Such a model allows non-adiabatic couplings between the states to be included. CASSCF calculations used in this work provide reliable quantum chemical information for the model and the calculated photoelectron spectrum shows good agreement to experiment. The vibrational fine structure of both bands are reassessed and different assignments to those previously reported are detailed. The existence of a conical intersection between the ionised states is reported and its role in the dynamics of phenol upon ionisation is examined.