Combined rotation and multi-pulse spectroscopy

Combined rotation and multi-pulse spectroscopy CRAMPS... 

To measure high-resolution spectra of disordered samples, the anisotropy of the chemical shift must be eliminated in addition to the homonuclear dipole-dipole interaction. This can be achieved for abundant nuclei by combined rotation and multi-pulse spectroscopy (CRAMPS), which is the combination of homonuclear multi-pulse spectroscopy and MAS [Bur2, Ger2, Sch6]. In Fig. 3.3.13, H spectra of monoethyl fumarate are compared for different NMR techniques [Brol]. Only the combination of MAS and multi-pulse excitation produces a high-resolution spectrum of the polycrystalline powder. 

Lesage et al. have shown that the resolution of the proton NMR spectroscopy of powdered solids can be improved significantly when multi-pulse sequences are employed [44a]. In the approach based on combined rotation and multipulse spectroscopy (CRAMPS) (Figure 7.9) the problem of dipolar line broadening is usually overcome. 

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