The 1320-nm excited FT-Raman spectra of lightly iodine-doped trans-polyacetylene

The FT-Raman spectra of trans-polyacetylene films doped lightly with iodine were obtained with the 1320-nm laser line. The observed Raman bands are attributed to positively charged domains created by acceptor doping. The observed Raman wavenumbers of the ν₂ (CC stretch), ν₃ and ν₄ bands (mixed of CC stretch and CH in-plan bending) of iodine-doped form are slightly higher than those of the corresponding bands of pristine trans-polyacetylene, whereas the contrary is the case for ν₁ band (C=C stretch) of iodine-doped form. In particular, these upshifts of the ν₂ and ν₃ bands are distinguished from the downshifts of these bands in donor doping. The origin of doping induced Raman bands is discussed in terms of solitons and polarons.