H-2-NMR spectroscopy is employed to investigate the orientational order in
the nematic and smectic A, B, and G phases formed by 4-(2-methylbutyl)pheny
l-4'n-heptylbiphenyl-4-carboxylate (7BEF5). The dynamics of the aromatic mo
lecular core is studied in a temperature interval including the S-A - S-B t
ransition, by the analysis of the deuterium Zeeman and Quadrupolar relaxati
on times with the rotational diffusion model.