Abstract
The molecular dynamics in some chiral smectic phases is studied by means of the solid-state ^<13>C-NMR spectroscopy and the high frequency dielectric measurements. The samples used are an antiferroelectric liquid crystal (S)-MHPOBC and a ferroelectric liquid crystal (S)-DOBAMBC. In ^<13>C-NMR measurements of (S)-MHPOBC, the spin-lattice relaxation time T_1 of the phenyl core part has a minimum at the temperature region of SmC_A^* in its temperature dispersion curve. Since the Ti minimum occurs at ω_0τ_c〜1, the correlation time (τ_c) of the molecular motion, which is to correspond to the molecular rotation around its long axis, could be estimated at about 10^<-8>sec. The activation energy of the molecular motion of phenyl core part in SmC_A^* estimated by the NMR measurements is larger than that in SmA, because of the stronger hindrance of the molecular rotation in SmC_A^*. As for (S)-DOBAMBC, the temperature dependence of T_1 shows that the activation energy in SmA is larger than in SmC^* for most of the carbon nuclei.
