Identification of Four C40 Isomers by Means of a Theoretical XPS/NEXAFS Spectra Study.

XPS and NEXAFS spectra of four stable C40 isomers [29( C2), 31( C s), 38( D2), and 39( D5 d)] have been investigated theoretically. We combined density functional theory and the full core hole potential method to simulate C 1s XPS and NEXAFS spectra for nonequivalent carbon atoms of four stable C40 fullerene isomers. The NEXAFS showed obvious dependence on the four C40 isomers, and XPS spectra are distinct for all four isomers, which can be employed to identify the four stable structures of C40. Furthermore, the individual components of the spectra according to different categories have been investigated, and the relationship between the spectra and the local structures of C atoms was also explored.