Molecular motions from two‐dimensional NMR of powders: Comparison of rotational jumps and diffusive reorientations

Abstract

Abstract With the two‐dimensional (2D) exchange NMR experiment on polycrystalline or amorphous solids it is possible to study reorientations in the slow motion limit. Anisotropic interactions lead to 2D powder spectra exhibiting characteristic singularities (“ridges”). From such a powder spectrum the relative orientations of a coupling tensor at the beginning and at the end of the mixing time can be measured without reference to any model of reorientation. The method is demonstrated for hexamethylbenzene and linear polystyrene.