Freezing of intramolecular motion around the chiral center of an antiferroelectric liquid crystal as evidenced by damped transient oscillations in C-13-H-1 cross polarization

Transient oscillations in C-13-H-1 cross-polarization dynamics in NMR is st udied for an antiferroelectric chiral smectic liquid crystal MHPOBC. Decay time of oscillation, which is determined by proton spin-diffusion, probes i ntramolecular motions. Different behaviors are found for the chain conforma tional motions around the chiral center in the paraelectric smectic A(S-A) and the antiferroelectric chiral smectic CA(S*(CA)) phases: Intramolecular motion of the chiral chain in the SA phase is Frozen in the S*(CA) phase. T his enables a large transverse dipole moment of a molecule to come out.