Frank-Condon approach for optical absorption and resonance Raman scattering intrans-polyacetylene

The Frank-Condon approach for resonance Raman scattering and optical absorption was used to explain the dispersion effect for the C=C stretch mode in trans-${\left(\mathrm{CH}\right)}_x$ quantitatively. The results are consistent with disturbed and undisturbed areas in the polymer. The Frank-Condon electron-phonon coupling constant was found 3.9 eV/Å, and the anomalous broad resonance cross section is interpreted as uncertainty broadening due to soliton-antisoliton generation from excited electron-hole pairs.