High-resolution proton methods for polymers, MAS and CRAMPS

10 High-resolution proton methods for polymers, MAS and CRAMPS 

In the preceding section, we discussed methods of suppressing dipolar interactions as a means of eliminating spin diffusion in relaxation measurements, but dipolar interactions are also the principal source of line-broadening in solid-state spectra, and therefore suppression of dipolar interactions also offers the possibility of obtaining high resolution spectra of solids in which chemical shift information is discernible. It is this, rather than the suppression of spin diffusion that has been the motivation in the development of these techniques, particularly the multiple pulse sequences. 

CRAMPS is an extremely demanding technique requiring a spatially homogeneous irradiation field and a very high degree of spectrometer stability, both in timing and phase. For a recent survey of the specific experimental requirements and some of the measures to overcome them see the article by Maciel et al. [130]. In common with other solid-state techniques, development of pulse sequences that are more tolerant of spectrometer imperfections [131] 

---