NUCLEAR SPIN RELAXATION IN LIQUID AND SOLID METHANE: ISOTOPE EFFECTS

Abstract

The deuteron spin–lattice relaxation time T₁ and spin–spin relaxation time T₂ have been studied in CD₄ and CD₃H between 55 °K and 110 °K. T₁ was found to increase very slowly with temperature over the entire temperature range for CD₄ with no measurable change being observable at the melting point. Since the deuteron spin relaxation is produced by intramolecular quadrupolar interactions, these results are in strong disagreement with the Debye rotational diffusion model often used to describe molecular reorientation. These results have been used to reanalyze the proton T₁ data for CH_4−nD_n previously given by Bloom and Sandhu. The contributions to T₁ from intermolecular dipolar interactions were found to be in close agreement with theory. Contributions from the spin–rotation interaction were found to be extremely small or zero in this temperature range. The effects of translational diffusion on the proton and deuteron T₁ and T₂ just below the melting point are also discussed.