Comparative He I and He II photoelectron spectroscopic studies of the benzoyl halides

Abstract

The He I and He II photoelectron spectra of benzoyl fluoride, benzoyl chloride and benzoyl bromide have been recorded and subjected to a relative band-intensity analysis. A comparison of experimental intensity data with the results of theoretical photoionization cross-section calculations is combined with a composite-model approach in interpreting the spectra. This interpretation supports the photoelectron-spectral assignments provided by appropriate molecular-orbital calculations. The low-ionization-energy regions of the benzoyl chloride and benzoyl bromide spectra comprise the localized benzene and non-bonding oxygen and halogen orbitals, while the corresponding fluorine orbitals are embedded in the band structure observed at higher ionization energy.