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

The FT-Raman spectra oftrans-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 pristinetrans-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.