An experimental and theoretical study of the valence shell photoelectron spectrum of butadiene

The valence shell photoelectron spectrum of butadiene has been studied using He I, Hen and synchrotron radiation. In addition to the main bands associated with the single-hole states, complex satellite structure due to many-electron effects has been observed in the inner valence region. Two variations of the many-body Green function method have been employed to evaluate the ionization energies and pole strengths of all valence states and the results have facilitated an interpretation of the experimental spectra. Photoelectron angular distributions and branching ratios have been measured using synchrotron radiation in the 12-120 eV range. Vibrational structure has been observed in several of the photoelectron bands excited with He I radiation and analyses have been performed for the X(2)B(g), (CBu)-B-2 and E(2)A(g) ionic states.