Study of Motion of D2O in Ba(ClO3)2D2O by Transient NMR

Deuteron spin lattice relaxation time T1 and the reorientation rate of D2O have been measured at various temperatures on a single crystal of Ba(ClO3)2D2O by transient nuclear magnetic resonance method. Temperature dependence of T1 is similar to that of corresponding proton resonance but three to four orders of magnitude smaller than the latter. From the slope of logT1 vs. 1/T curve, activation energy of reorientation of D2O of 6.5–6.8 kcal/mol is obtained in agreement with that from line width transition. Theoretical values of T1 minima were in good agreement with the observed. Direct measurement of reorientation rate is made by observing a signal recovery from saturation of one of the two deuteron sites of D2O due to the exchange with unsaturated spins at the other site. The Arrhenius plot of the reorientation rate down to −170°C determined in this manner smoothly connects to that derived from the line width transition. A revision of the previous treatment of line width change is described and the reorientation rates of Ba(ClO3)2D2O are re-evaluated according to this method. A satisfactory agreement is found among the conclusions from the three different types of experiment, T1, the line width transition and the directly measured reorientation rate. The motion is a random reorientation of D2O with a rate governed by an activation process of 7 kcal/mol.