Momentum-dependent dielectric function of the cis-transoid conformation of cis-polyacetylene

The electronic structure of the oriented cis-transoid conformation of cis-polyacetylene has been investigated by electron-energy-loss spectroscopy. The energy-loss spectra have been measured in an energy range from 0 to 48 eV with a momentum transfer varying from 0.1 to 0.8 A${̊}^{\mathrm{-}1}$. Using a Kramers-Kronig analysis, the momentum-dependent dielectric functions parallel and perpendicular to the chain axis were derived and compared to band-structure calculations.