Abstract
The optical properties of undoped polyacetylene are discussed. Specular reflection spectra from freestanding cis- and trans-(CH)x films are compared to transmission spectra from thin films. It is shown that the ‘‘true’’ absorption spectrum of well ordered, long chain trans-polyacetylene has a well defined 0–0 transition at 12 000 cm−1 followed by vibrational structure. This suggest an excitonic assignment for the lowest energy optical transition. In thin films conjugation length dispersion is shown to be a major source of disorder dominating the optical properties. (AIP)