PHOTOELECTRON SPECTRA OF THE ALKYL PHENYL DISULFIDES

The He I and He II spectra of the alkyl phenyl disulfides were recorded and interpreted in terms of a composite-molecule model in which the sequence of the first four ionisation energies is: πs—ns < ns < π < πs + ns . This sequence is contrary to the STO-3G* calculations, but in agreement with the more extensive 3–21G* calculations. Furthermore, analysis of the intensity variations on going from He I to He II radiation validates the composite-molecule model and therefore suggests that the sulfur lone-pairs adjacent to the alkyl moiety are localised on the sulfur atom, whereas the sulfur lone-pairs adjacent to the ring are delocalised within the π system of the phenyl ring.