Distinguishihg ionization from sulfur p-type lone pair orbitals and carbon π-molecular orbitals by he I/He II photoelectron spectroscopy

He I and He II photoelectron spectra of methylthiomethylbenzene (2), 2-(1-nethylethylthio) ethylbenzene (3), 1-naphthalenemethanethiol (4), 1,1-dimethylethylthiobenzene (5), benzenethiol (6), and methylthiobenzene (7) are reported. Comparison of the He I and He II band areas for each compound provide a reliable basis for assigning the bands as due to photoionization from a carbon π-molecular orbital, sulfur p-type lone pair orbital, or mixed orbital.Ionization from a molecular orbital localized on sulfur results in a large decrease in intensity using He II compared with He I as the source relative to ionization from carbon π-molecular orbitals. Mixed orbitals with both sulfur and carbon character also give rise to diminished intensities in the He II versus He I spectra relative to pure carbon orbitais, but proportionately less decrease than pure sulfur orbitais.