Proton spin relaxation in dilute methane gas: a symmetrized theory and its experimental verification

Nuclear spin relaxation in low density methane gas is investigated theoretically and experimentally. A theory is developed in which full account is taken of the tetrahedral symmetry of the molecule. On the basis of the theory, a new type of 'relaxation rate spectroscopy' is proposed. Non-exponential relaxation is predicted to occur at low densities when the nuclear Larmor frequency is tuned to a centrifugal distortion splitting. (author)