Solitons in Polyacetylene: Effects of Dilute Doping on Optical Absorption Spectra

A joint theoretical and experimental study of the effects of dilute doping on the optical absorption spectra of trans-polyacetylene, trans-${\left(\mathrm{CH}\right)}_x$, is presented. It is shown that the optical transition between a band state and the soliton level is considerably enhanced. However, the existence of a soliton kink strongly suppresses the interband transition. The agreement between theory and experiment supports the applicability of the soliton model to trans-${\left(\mathrm{CH}\right)}_x$.