Abstract
When nuclear spin-lattice relaxation in solids is due to rapid random rotation of methyl groups, the Zeeman relaxation can be nonexponential. This is because the magnetization is dynamically coupled to the so-called rotational polarization. It is shown that rotating the sample perpendicular to the magnetic field with angular velocity large compared with the relaxation rate decouples these parameters, resulting in an almost exponential Zeeman relaxation close to that predicted by the spin-temperature theory.