Static Broad Line Experiments

Among several indicators of motional state of organic solids H linewidths has been used from very beginning of solid-state NMR. However, inherently low resolution of H MAS NMR spectra caused by the very strong homonuclear interactions and relatively low MAS speed lead to a very limited application of H MAS NMR for studies of mobility.1 A 2D wideline separation (WISE) experiment correlates carbon chemical shifts recorded under MAS with broad H lines.1,24 As a result a broad ll lines are separated in the components corresponding to the 13C sites in their close proximity. For mobile domains in a sample, the H - ll coupling are relatively weak which leads to relatively narrow 11 static lines. The opposite is observed for the rigid domains. 

For a quadrupolar nuclide with a nonintegral spin (/ = 5, " 5, 5, or in high magnetic field, the narrowest static-sample resonance corresponds to the — l/2<- l/2 (or, 1/2) transition. This transition is broadened only in second-order by the quadrupole interaction. The line shapes from the other transitions are typically so broad that they often cannot be effectively excited. Therefore one usually is performing a selective experiment, in the sense that only a particular transition within the allowed manifold of transitions is observed. Under these circumstances the Hartmann-Hahn [11,32,33] match condition becomes... 

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