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The anisotropy of the translational self-diffusion tensor in the smectic-A (0\\)/0j_) = 0.3) and smectic-C phases of terephthal-fet5~4-w-butylaniline has been determined by multipulse NMR. The experimental results are interpreted in terms of a pseudolattice model with anisotropic potential barriers which seems to provide a better description of the physical situation than the "two-dimensional-liquid" model.

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Ultraslow reorientational motions of the H2PO4 and H2SeO3 groups have been studied in KH2PO4, RbH2PO4, CsH2PO4, LiH3(SeO3)2, NaH3(SeO3)2, KH3(SeO3)2, and CsH3(SeO3)2 by dipolar and rotating frame proton spin–lattice relaxation measurements. The measured values of the reorientational correlation times change from about 10−3 sec at room temperature to about 10−5 sec at 100°C. The activation energies for the hindered rotation of the H2PO4, respectively, H2SeO3 groups are controlled by the size of the cation rather than by the strength of the O–H···O bonds, and vary from 0.4 to 1.4 eV. In contrast to the case of ice this slow reorientational process dominates the dc protonic conductivity of both the KH2PO4 and the NaH3(SeO3)2 group of hydrogen bonded crystals.