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

The photoelectron spectrum of the chlorobenzene molecule has been studied u sing both monochromated synchrotron radiation with photon energies between 15 and 120 eV and HeI radiation at 21.22 eV. Photoelectron angular distribu tions and branching ratios have been determined over the entire energy rang e studied. Theoretical investigations have been performed using ab initio S CF and many-body Green's function methods to evaluate wave functions, bindi ng energies and relative intensities. The ADC(3) calculations of binding en ergies and pole strengths were particularly important for the interpretatio n of the inner valence spectrum where electron correlation effects are foun d to be important. The main part of the photoelectron spectrum is similar t o that of benzene but some of the bands are characteristic of the chlorine atom. The Cooper minimum of the Cl 3p orbital is clearly reflected in some of the bands and is used to assess the mixing between ring orbitals and chl orine atomic orbitals, The HeI-excited spectra show extensive vibrational s tructure in the (X) over tilde B-2(1), (A) over tilde (2)A(2), (B) over til de B-2(2), (C) over tilde B-2(1) and (K) over tilde (2)A(1) photoelectron b ands. The vibrational structure is analysed in detail and compared to resul ts obtained from multiphoton ionisation photoelectron spectroscopy. (C) 200 0 Elsevier Science B.V. All rights reserved.