An experimental and theoretical study of the valence shell photoelectron spectrum of the benzene molecule

The photoelectron spectrum of benzene has been studied using HeI and synchrotron radiation for the ionisation. The study involves all main bands associated with the single-hole valence states, as well as satellite structure observed in both the outer and the inner valence regions, due to many-electron effects. Many-body Green's function calculations have been carried out employing the ADC(3) approach, and theoretical predictions for the ionisation energies and pole strengths (relative intensities) have been obtained, thus facilitating the interpretation of the experimental results. Photoelectron angular distributions and branching ratios have been determined using monochromated synchrotron radiation in the photon energy range 12-120 eV. HeI excitation has been used to obtain highly resolved spectra and vibrational structure has been studied in the X E-2(1g), A E-2(2g), C E-2(1u), E B-2(1u) and F (2)A(1g) ionic states. In the first two bands excitations of Jahn-Teller active modes are found to be important and very good agreement is found with recent theoretical studies of the vibronic structure. (C) 1997 Elsevier Science B.V.