Calculated optical properties of PPP-oligomers

We have calculated the frequency dependent complex dielectric tensor for bi - and terphenyl within the framework of density functional theory. The good agreement with experimental data confirms that the anisotropy in the optic al absorption can be well understood within the band picture. We predict th e absorption behavior of ordered films with various chain orientations with respect to the substrate surface. We compare the optical properties of the molecular and the crystal phase. Furthermore, we show differences between the absorption spectra of poly(p-phenylen) (PPP) and its oligomers, respect ively.