Spin lattice relaxation rates of tunnelling CD3 groups

The spin lattice relaxation rates of deuterated methyl groups are calculated for threefold and sixfold potentials. It is shown that it should be possible to determine the symmetry of the potential hindering the methyl groups from deuteron spin lattice relaxation experiments. The temperature dependence of the spin lattice relaxation rates is discussed using a simple model. The similarities and the differences between proton NMR and deuteron NMR are pointed out. The main difference is thatEaEb transitions are forbidden by spin selection rules in case of CH₃, but not for CD₃. Therefore, and due to the fact that the quadrupolar interaction is a single particle interaction, deuteron NMR allows the study of the rotational dynamics of single methyl groups.