Fakultät für Physik, Universität Freiburg, D78 Freiburg, Germany;Physik-Department, Technische Universität München, D8046 Garching, Germany;Lehrstuhl für Theoretische Chemie, Technische Universität München, D8 München, Germany
Abstract:
A theory of vibronic coupling in molecules is presented and applied to butatriene. The energies and coupling constants which enter the calculation are computed using ab initio Hartree—Fock and many-body methods. The influence of the energy splitting and the coupling constants on the calculated spectrum is discussed. It is definitely shown that the “mystery band” in the photoelectron spectrum of butatriene arises from the vibronic coupling between the electronic states 2B3g and 2B3u. To reproduce the experimental observations it is essential to include in the calculation both totally and non-totally symmetric vibrational modes.