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_nF_2n+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.

Key Words:

• fluorine
• UPS
• NEXAFS
• vacuum-UV spectra
• electronic structure
• poly(hexal1uoro-I 3-butadiene) PTFF
• C₆₀F _x C₇₀F _x CF
• C₂F
• C₆F