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

Abstract

We report measurements of ¹⁹F NMR relaxation times T₁, T_1ρ, T_1D, 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 T_1ρ 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 τ_IS as a function of field and found good agreement with our theoretical calculation of τ_IS.