Nuclear spin–lattice relaxation and site symmetry in phase II of solid CH4

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Abstract
On the basis of Nijman’s theory of relaxation in solid CH4, T1 measurements at low T are here recognized to be important for determining the exact symmetry of the orienting field in phase II. An experiment in the range 60–100 MHz would check unambiguously the EJK model prediction of a D2d site symmetry. The existing T1 data are shown to agree with this latter as far as the dependence on the Larmor frequency, the dependence on temperature and the T1 behavior during the fast conversion of free‐rotating molecules are concerned. The twofold reorientations are probably responsible for the spin–lattice relaxation at low T.