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 rev iewed, and in particular those encountered in NMR experiments. The fai lure 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. Furthe rmore, we discuss the dramatic (I = 1) solid echo signal loss with dec reasing temperature which is observed in solid D2, but not for solid H -2. A theory of the solid echo damping through orientational fluctuati ons is developed. This theory accounts for the observed solid echo dec ay in D2 as a function of the pulse spacing time tau and leads to an e stimation of the order parameter fluctuation amplitude and the correla tion time tau(c). However, the theory cannot account for the loss of s pin (as determined from Curie's law), which must occur for very small values of tau that are not covered by the theory.