NMR observations of molecular motions and Zeeman–quadrupole cross relaxation in 1,2-difluorotetrachloroethanea)

Abstract

We report measurements of 19F NMR relaxation times T1, T1ρ, T1D, and T2 in the plastic crystal CFCL2–CFCL2. From the data near the melting point, we obtain the jump time for translational self-diffusion. At lower temperatures, we observe on the cold side of the T1 and T1ρ minima an unusual field dependence which is substantially less than the normal field-squared dependence. We also observe a reduction in T1 near 40 MHz due to cross relaxation between the Zeeman levels of the 19F spins and quadrupole levels of the 35Cl and 37Cl spins. We measured the cross relaxation times τIS as a function of field and found good agreement with our theoretical calculation of τIS.