The NMR measurement of polyacetylene (mostly concerning T1)

The NMR measurement of polyacetylene was performed. The NMR absorption wave form gives information on crystal structure. Measurement of a transpure sample at 4.2 K gives a structure which is consistent with those given by Baughmann et al. and Shimamura et al. The frequency dependence of the spin lattice relaxation time T1 was measured, and the conformity to square-root law was observed. The temperature dependence upon T1 was measured by the π, π/2 pulse method, then minus 1/4 the power dependence of temperature was seen. This dependence can be explained by the scattering of neutral soliton by acoustic phonon. The temperature (T) dependence of T1 of Br2-doped samples was measured. The relation that the product of T1 and T is constant was found in the range between 4.2 and 300 K. It is suggested that the electric conductivity is due to charged soliton. The NMR T1 measurement of 13C by the CP method was also performed. The product of T1 and T was also constant. In case of a AsF5-doped sample, the contribution of Bloembergen type by molecular rotation of chain is suggested. (Kato, T.)