K. H. LAUAND S. H. LIN
2458
Finally, we come to the frequency dependence of T1. The unambiguous prediction of eq 1 is that TI is Experiments on compound I proportional to wl/'. (PAA) reveal that
nematic to the isotropic phase since the diffusion constant is known to drop by a factor of about 3.26 I n conclusion, we find that the dependence of T I on molecular alignment and on temperature does not support a rotational mechanism for spin relaxation T1 N A Bw"' (3) and that the frequency dependence of TI does not disand appear to provide support for the theory. Howtinguish between the rotational and translational mechever, the theory of spin relaxation by translational difanisms. An experiment is called for, perhaps making fusion is not without a frequency d e p e n d e n ~ e . ~I n~ use of totally deuterated liquid crystals, to separate fact, Harmon and Muller have demonstrated that24j26 the inter- and intramolecular contributions to spin relaxation.27
+
(4) where r is the mean time between diffusion jumps and a is of order unity. For UT
