Pinned mode in polyacetylene: A distribution of soliton-lattice densities.

The pinned mode in optically excited polyacetylene Is a vibrational envelope with a width of =500 cm centered at 500 cw,". The width of this mode has been attributed to single solitons interacting with a wide range of pinin par etrs. The constancy of the envelope for polyacetylene prepared by disparate methods (Shirakawa and Durham)d Cis-trans ratios, casts doubt on this concept as the underlying mechanism for the shape of this vibration. The results of the work discussed here indicate that a more likely cause for the observed envelope is a superposition of spectra 6f various soliton lattice densities, all pinned with the same pinning mechanism. )