VALENCE AND CORE-SHAKEUP PHOTOELECTRON-SPECTRA OF SOLID POLYACETYLENEAND RELATED FREE MODEL MOLECULES

The x-ray photoelectron spectrum of polyacetylene and the related mode l molecules ethene, 1,3-butadiene, and 1,3,5-hexatriene are studied wi th respect to the valence and C 1s shakeup regions. The interpretation of the polyacetylene spectra is accomplished by a detailed assignment of the gas-phase results. It is shown that the development of the ban d structure of solid polyacetylene can be followed step by step for th e molecules. The electron correlation is shown to play a dominant role for the description of the inner-valence structures. The outermost ba nd centered at 3 eV below the Fermi level is unambiguously assigned to the band structure arising from the out-of-plane pi-type molecular or bitals. The polyacetylene shakeup spectrum exhibits several structures that have been assigned by comparison to experimental results and -of -differential-overlap-configuration-interaction calculations on the mo del molecules.