Electronic structures and chemical bonding of fluorinated fullerenes studied by NEXAFS, UPS, and vacuum-UV absorption spectroscopies

The chemical bonding and the electronic structures of C60Fx and C70Fx were investigated by near edge X-ray absorption fine structure (NEXAFS) spectroscopy and UV photoemission spectroscopy (UPS), which are useful methods for examining the unoccupied and the occupied states, respectively. With these results and XPS measurements, we derived the electronic energy diagram of C60Fx and discussed the change of the electronic structure from that of C-60 by fluorination. The energies of the LUMO and the Fermi level of solid C60F48 were estimated to be -5.0 and -5.4 eV below the vacuum level, indicating that highly doped C60Fx, is a strong electron acceptor. The electronic absorption spectra of C60Fx solutions deep into the vacuum-ultraviolet reg ion were also measured, and the isomerism of C60Fx, was discussed by comparing the observed results with theoretical simulations.