THE ORIENTATIONAL GLASS (KI)(0.56)(NH4I)(0.44) STUDIED BY I-127 NUCLEAR-MAGNETIC-RESONANCE

Single crystals of the orientational glass (KI)(0.56)(NH4I)(0.44) have been studied using iodine NMR for temperatures 1.8 K < T < 300 K. Two -dimensional spectroscopy has shown that the quadrupole-perturbed cent ral transitions are predominantly inhomogeneously broadened. The orien tational glass transition is already accompanied by a considerable inc rease of that broadening in the regime of fast motion. Evidence for a random-field smearing of the random-bond-induced freezing process is o btained. Measurements of the spin-lattice relaxation time reveal the e xistence of a broad distribution of orientational correlation rimes at low temperatures.