Optical spectra and neutral soliton in segmented polyacetylene

We have measured the doping induced optical absorption in segmented poly acetylene, [CDH_y]_x, in which either 15% or approximately 27% sp³-bonded CDH units. These sp³ defects, which can be called "conjugation-interrupting" defects have an average spacing considerably less than the length of a soliton. In order to introduce the charged soliton excitation, all samples were doped with iodine by in-situ vapor doping technique with various dopant levels. For a sample with 27% sp³ hybridization, we have found a new broad band around 1.12 eV with relatively lower intensity for lower sp³. We assigned this band as an absorption due to the neutral solitons. The optical properties of deuterated polyacetylene with sp³ defects including the comparison with ordinary polyacetylene, (CH)_x, will be discussed.