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

The x-ray photoelectron spectrum of polyacetylene and the related model molecules ethene, 1,3-butadiene, and 1,3,5-hexatriene are studied with 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 band structure of solid polyacetylene can be followed step by step for the molecules. The electron correlation is shown to play a dominant role for the description of the inner-valence structures. The outermost band centered at 3 eV below the Fermi level is unambiguously assigned to the band structure arising from the out-of-plane pi-type molecular orbitals. The polyacetylene shakeup spectrum exhibits several structures that have been assigned by comparison to experimental results and incomplete-neglect-of-differential-overlap-configuration-interaction calculations on the model molecules.