Magic-angle spinning signal enhancement

Z. Yao, H. T. Kwak, D. Sakellariou, L. Emsley and P. J. Grandinetti, Sensitivity enhancement of the central transition NMR signal of quadrupolar nuclei under magic-angle spinning. Chem. Phys. Lett., 2000, 327,85-90. 

P. K. Madhu, K. J. Pike, R. Dupree, M. H. Levitt and M. E. Smith, Modulation-aided signal enhancement in the magic angle spinning NMR of spin-5/2 nuclei. Chem. Phys. Lett, 2003, 367,150-156. 

We have seen how by magic-angle spinning (MAS) and high-power decoupling the resolution is rendered similar to that in the solution phase. The intensity of signals due to less abundant nuclei is enhanced by the use of cross-polarization (CP) pulse sequences. Excellent spectra of a variety of nuclei in the solid state have been obtained... 

Owing to the chemical composition of silica, two nuclei are usually analyzed. They are H, as abundant spin and Si as a rare one. Numerous experiments have been done by cross polarization (CP) between proton and silicon nuclei and magic angle spinning (MAS). As it is a classical method analyzed elsewhere [2], it is not described here in details. It is only necessary to notice that the silicon signal is enhanced if the distance to proton is short enough to provide an efficient dipolar interaction. So this means that the method allows to distinguish the different types of hydroxylated silicon species, but also... 

Brauniger, T., Madhu, P.K., Pampel, A., and Reichert, D. 2004. Application of fast amplitude-modulated pulse trains for signal enhancement in static and magic-angle-spinning Ti-NMR spectra. Solid State Nucl. Magn. Reson. 26 114—120. 

Cross-polarization (CP) combined with magic-angle spinning (MAS) technique has been used for the high-resolution solid-state C NMR study of occluded templates in mazzite-type stractures like ZSM-5 and SAPO-37 [98K1, OOGlj. The C MAS NMR signals of carbon sites of the template TPA were enhanced by CP, which... 

---