Proton NMR study of the molecular motions in smectic-C*ferri and anti-ferroelectric mesophases

We report the first study of molecular dynamics in S-C gamma* (ferrielectri c) and S-CA* (anti-ferroelectric) mesophases of a liquid crystal: by means of proton NMR relaxation. The relaxation dispersion detected in both S-C ga mma* and S-CA* mesophases is compared with the observed for the S-A and S-C * phases of the same compound, which is similar to those observed in previo us studies. However, to describe the relaxation behaviour detected in both S-C gamma* and S-CA* mesophases we had to include an additional relaxation mechanism. Considering the frequency range where it is observed, this mecha nism may be related to the antiphase azimuthal mode previously detected by dielectric permittivity studies.