A H-2 NMR-STUDY OF ORIENTATIONAL ORDER AND SPIN RELAXATION IN THE MESOGEN P-HEXYLOXYBENZYLIDENE-P'-FLUOROANILINE

H-2 NMR measurements of orientational order and spectral densities in the nematic, smectic A and smectic B phases of p-hexyloxybenzylidene-p '-fluoroaniline (FAB-OC6) deuterated in the benzylidene methine group and in the aniline ring are reported. The orientational order paramete rs obtained indicate a high order of the aromatic core in the smectic phases. The Wimperis pulse sequence was used to measure the Zeeman and quadrupolar spin-lattice relaxation times at the frequency of 46.04 M Hz. The spectral densities are discussed within rotational diffusion m odels for the reorientational motions, taking also into account intern al rotations and collective fluctuations.