SOLID H-2 AND D(2) - REMARKABLE DIFFERENCES IN SOME NMR PROPERTIES

The differences in the observed properties of solid H-2 and D2 are reviewed, and in particular those encountered in NMR experiments. The failure to detect a sharp NMR (I = 1) impurity ''isolated pair'' spectrum in p-D2 is discussed in terms of a larger crystalline field than in H-2, where an intense and sharp pair spectrum has been observed. Furthermore, we discuss the dramatic (I = 1) solid echo signal loss with decreasing temperature which is observed in solid D2, but not for solid H-2. A theory of the solid echo damping through orientational fluctuations is developed. This theory accounts for the observed solid echo decay in D2 as a function of the pulse spacing time tau and leads to an estimation of the order parameter fluctuation amplitude and the correlation time tau(c). However, the theory cannot account for the loss of spin (as determined from Curie's law), which must occur for very small values of tau that are not covered by the theory.