Polarized resonant Raman spectra of fully orientedtrans-polyacetylene: Experiments and theory

Experimental polarized resonant Raman scattering spectra of oriented trans-(CH${)}_{\mathrm{x}}$ samples are presented at different excitation wavelengths together with theoretical evaluations. The experimental spectra are highly polarized and show different and sample-dependent depolarization ratios for ${\lambda }_L$=647.1 nm and ${\lambda }_L$=457.9 nm. A shift in the peak positions of the double- and single-bond vibrational frequencies is observed for ${\lambda }_L$=457.9 nm when the polarizations of the incident and/or scattered light are perpendicular to the chain axis with respect to those obtained when both polarizations of light are parallel. The experimental features are interpreted with the model proposed which assumes that trans-(CH${)}_{\mathrm{x}}$ is formed by different conjugation length segments. Also, the estimated depolarization ratios are in reasonable agreement with the calculated results.