Raman spectra of heavily sodium-doped trans-poly acetylene and the radical anions of diphenylpolyenes and dithienylpolyenes

The Raman spectra of trans-poly acetyl ene doped with sodium (Na) at the maximal level have been measured with excitation laser lines between 488.0 and 1064 nm. These spectra have been compared with those of model compounds, i.e., the radical anions of α, ω-diphenylpolyenes (Ph-(CH=CH).-Ph, n = 3, 4) and a, co-di-2-thienylpolyenes (Th-(CH=CH).-Th, n = 3 and 4). The similarity between the Raman spectra of Na-doped polyacetylene and those of the radical anions indicates that the observed bands of Na-doped polyacetylene arise from charged domains generated by Na-doping. The observed large wavenumber dispersion of the C=C stretching vibration of the charged domains suggests a broad distribution of localization lengths in the charged domains.