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

The valence shell photoelectron spectrum of bromobenzene has been studied, both experimentally and theoretically, in order to characterise the main ba nds due to single-hole states and to assess the importance of electron corr elation in the formation of satellite states. Synchrotron radiation has bee n employed to measure photoelectron angular distributions and branching rat ios in the photon energy range 16-120 eV, and high-resolution spectra have been recorded using HeI excitation. The results indicate that the 2b(1) and the 6b(2) lone-pair orbitals retain their atomic properties to a substanti al degree, and that the photoionisation dynamics associated with these two orbitals exhibit effects due to the presence of a Cooper minimum. The resul ts for bromobenzene are compared with corresponding data for benzene and it appears that several of the orbitals remain essentially unperturbed by the introduction of the halogen atom. The high-resolution spectra have enabled detailed assignments to be made of the vibrational structure displayed in the (X) over tilde(2)B(1), (A) over tilde(2)A(2), (B) over tilde B-2(2), (C ) over tilde(2)B(1) and (K) over tilde(2)A(1) photoelectron bands. Two vari ations of the many-body Green's function method have been employed to evalu ate the ionisation energies and pole strengths (relative intensities) of al l valence states. These predictions have helped assign and interpret the fe atures caused by configuration interaction. (C) 2000 Elsevier Science B.V. All rights reserved.