Complete determination of the relaxation matrix of CH3groups in solids by means of experiment-dependent NMR relaxation measurements

Abstract

The coupled relaxation of the Zeeman magnetization and the rotational polarization have been derived for a polycrystalline sample consisting of methyl protons and other protons, assuming the rapid reorientation of the methyl groups to be the dominant relaxation mechanism. The observed relaxation behaviour is found to depend on the preparation of the spin system, because different initial values of the rotational polarization can be obtained. Moreover the behaviour of the Zeeman relaxation can be altered by an external rotation of the sample, or by a sudden flip of the sample over an angle of 180 degrees , because this influences the coupling between the magnetization and the rotational polarization. The experimental results are verified on a polycrystalline sample of 2,6-dimethylphenol at room temperature.