Cross polarization CP/MAS

Figure 45 P MAS single-pulse (FT-MAS) and cross-polarization (CP-MAS) spectra...

These two techniques are called cross-polarization (CP) and magic angle spinning (MAS) in combination, these are thus called CP-MAS. 

The majority of double-resonance solid-state NMR experiments involving spin-1/2 nuclei use transfer of nuclear polarization via dipolar cross polarization (CP) to enhance polarization of the diluted spins S with small gyromagnetic ratio ys and significant longitudinal relaxation time T at the expense of abundant spins I with large y, and short 7 [215]. Typically, CP is used in combination with MAS, to eliminate the line broadening due to CS A, as well as with heteronuclear decoupling. To achieve the / S CP transfer, a (n/2)y pulse is applied at the I spin frequency,... 

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... 

A suitable way to enhance NMR signals of nuclei with small magnetogyric ratios or low concentrations (rare spins 5) interacting with abundant spins I is the polarization transfer from the spin I to the spin S ensemble via a cross polarization (CP) experiment. This experiment is based on a double resonance technique, which can be applied in combination with MAS for the characterization of surface sites of solid catalysts and rigidly bound surface complexes. The pulse sequence used for CP experiments is demonstrated in Fig. 4. 

Fig. 4.32 Demonstration of the cumulative effects of techniques employed in C CP/MAS SSNMR spectroscopy on a sample of dideoxyinosine. (a) High-power proton decoupling combined with magic-angle spinning (MAS) and cross polarization (CP) (b) high-power proton decoupling and MAS at 5 kHz (c) high-power proton decoupling only and (d) conventional solution phase techniques. (From Bugay 1993, as modified by Byrn et al. 1999.)...

In addition to MAS and DD explained above, cross polarization (CP) is usually used in present solid-state high-resolution NMR measurements. This is... 

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