NMR relaxation study of hardening acid-base dental cements

The orientational glass studied by nuclear magnetic resonance

Single crystals of the orientational glass have been studied using iodine NMR for temperatures 1.8 K < T < 300 K. Two-dimensional spectroscopy has shown that the quadrupole-perturbed central transitions are predominantly inhomogeneously broadened. The orientational glass transition is already accompanied by a considerable increase of that broadening in the regime of fast motion. Evidence for a random-field smearing of the random-bond-induced freezing process is obtained. Measurements of the spin - lattice relaxation time reveal the existence of a broad distribution of orientational correlation times at low temperatures.