Spin-lattice relaxation by tunnelling motions of methyl groups in some organic compounds

The proton spin-lattice relaxation times, T₁, of methyl groups in (CH₃CO)₂O, CH₃COCl, CH₃ COBr and (CH₃)₂S₂ have been measured below melting points at 52 MHz. The observed T₁ minima display the presence of tunnelling rotation. From the fit of the experimental results the ground, the first excited state tunnelling frequencies and the energy difference between the ground and the first excited states of the compounds have been estimated.