High-Energy Spectroscopic Studies of the Electronic Structures of Organic Systems Formed from Carbon and Fluorine by UPS, Vacuum-UV Optical Spectroscopy, and NEXAFS: Poly(hexafluoro-1,3-butadiene) [C(CF3) = C(CF3)] n , Fluorinated Graphites (CF, C2F, and C6F), Perfluoroalkanes n-C n F2n+2, Poly(tetrafluoroethylene) (CF2) n , and Fluorinated Fullerenes (C60F x and C70F x )

Abstract

Various systems formed by carbon and fluorine were studied by UV photoelectron spectroscopy (UPS), vacuum-ultraviolet (VUV) optical spectroscopy, and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. New data were meawred for poly(hexat1uoro-1.3-butadiene) (PHFBD), which is actually poly(hexafluoro-2-butyne), and tluorinated graphitcs CF, C2F, and C6F. These data were analyzed together with reported data for n-C24F50, poly(tetratluoroethy1ene) (PTFE), and fluoninated fiillerenes C60F x and C70)F x . The electronic structures deduced from UPS, VUV optical spectra, and MO calculations could be understood in terms of degree of IS delocalization, inductive effects of F and CF3 groups, and the molecular conformation with possible steric hindrance. The ionization threshold energy of PHFBD (10.3eV) is the largest one for unsaturated systems. The well polarized NEXAFS spectra of CF and C2F were analyzed by the comparison with related compounds. The NEXAFS results of C6F showed that the F atoms are neither in molecular form nor covalently bonded to carbon atoms.