Fluorine Kα x-ray emission studies of fluorinated organic compounds

Fluorine K_α X-ray emission spectra have been measured and interpreted using UV photoelectron and X-ray photoelectron spectral data and the results of quantum-chemical calculations, for a series of fluorine-containing organic molecules: CH₃F, n-C₅F₁₂, polytetrafluoroethylene, tetrafluoroethylene, 4-XC₆H₄F (X = H, F, NH₂, NO₂), 1,3-difluorobenzene, 1,2,4,5-tetrafluorobenzene, 1,4-difluorobenzene, C₆F₅X (X = H, F, SCH₃, OCH₃, CN, NO₂, C₆F₅, P(OCH₃)₂), pentafluoropyridine, octafluoronaphthalene and 2,4-dinitrofluorobenzene, all in solid or gaseous states. It has been concluded that the fluorine 2pAO contribution to the highest occupied π-orbitals of the benzene ring and π-orbital of the ethylene bond is small: it is somewhat higher for a system of lower-lying π-orbitals and the highest for σ-orbitals. CH₃F is assumed to have hyperconjugation.