Carbon K-edge X-ray absorption near edge structure (XANES) spectra of evaporated films of poly-p-phenylenes and polyacenes were measured by use of synchrotron radiation. Only one dominant resonance associated with a Cls-to-x* transition was observed for each poly-p-phenylene, although there should exist several x* unoccupied orbitals which are energetically well separated from each other. These features were characterized by means of semi-empirical molecular orbital (MO) calculations based on the equivalent core approximation, which leads to a satisfactory agreement between the observed and calculated spectra. The calculations show that the x* orbitals, which are delocalized in the ground state, become localized by the creation of a CIS core hole. Spectral features of polyacenes, which are somewhat different from those of poly-p-phenylenes in their x* regions, indicate a lesser degree of I[* localization.

Polarization dependent XANES spectra were obtained by use of synchrotron radiation for oriented polyethylene and fluorinated polyethylenes: (1) elongated polyethylene (PE) film, (2) elongated poly(viny1idene fluoride) (PVDF) film, (3) poly(tetrafluoroethy1ene) (PTFE) film, (4) oriented evaporated film of hexatriacontane. CH3(CH,),,CH, as a model compound of PE, (5) oriented evaporated film of perfluoroeicosane, CF,(CF,),,CF, as a model compound of PTFE.Pronounced polarization dependence was observed for each compound, which allows unambiguous assignments of the XANES spectrum. Fluorination effects on the XANES spectra was also discussed

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The change of electronic structure at UV photopolymerization was studied by XANES and UPS for evaporated films of a long-chain diacetylene compound tricosa-10, 12-diynoic acid. The UPS spectra showed a large lowering of ionization threshold energy (from 7.0eV to ca. 5.2eV) due to the formation of a conjugated n electron system, as in our previous study of Langmuir-Blodgett films. The XANES spectra showed that the alkyl chains are inclined to the substrate surface, consistent with X-ray diffraction studies. The CIS + n* absorption showed a drastic change on photopolymerization, which could be well explained with CNDOjS molecular orbital calculations taking account of the hole formation using the equivalent-core approximation. From XANES studies, no essential discontinuity was found between the blue and red forms of the polymers formed.