Exciton-Forming Vibronic Optical Subbands and Their Inhomogeneous Broadening in Trans-Polyacetylene

A method has been established to prepare as-grown, about-10-µm-thick (CH) x films which show a reflection spectrum with two conspicuous triplet structures, one at 1.57, 1.69 and 1.81 eV originating from trans-form segments and the other at 2.07, 2.24 and 2.41 eV from cis-form segments. These exciton-forming vibronic optical subbands of triplet structure usually become somewhat blurred after the completion of cis-trans conversion; thermoreflectance measurements have been performed to restore the triplet structure clearly. By comparing the inhomogeneous broadening of the exciton-forming vibronic optical subbands in trans-(CH) x with that in poly( p -phenylenevinylene), the possibility of observing the luminescence spectra from trans-(CH) x segments under quasi-resonant conditions has been discussed.