NUCLEAR MAGNETIC RELAXATION STUDIES OF BENZENE IN ULTRAPURE NaX ZEOLITE.

In a sample of NaX zeolite with very low paramagnetic impurity, the temperature behaviour of the proton relaxation times T//1 and T//2 has been studied for different coverages of benzene, 1,3,5-trideuterobenzene and different mixtures of benzene and hexadeuterobenzene. For termperatures above 200K, T//1 is determined by the interaction of the protons with the residual paramagnetic impurities, which allows the estimation of translational diffusion coefficient of about 10** minus **7 cm**2s** minus **1 at room temperature. From the frequency dependence of the T//1-minimum average activation energies of 15kj/mol can be drawn for intermediate and 34kj/mol for full coverage. The data for the deuterated samples give the intra-and the intermolecular part and the contribution of the interaction with the paramagnetic impurities to the longitudinal relaxation rate can be drawn below 200 K. From these results for 3. 6 molecules in a large cavity, a mechanism of motion can be drawn the freedoms of which lie in the range of an isotropic rotational reorientaion.