Carbon-13 NMR imaging of solids with magic angle sample spinning.
The first 13C NMR imaging method suitable for rotating solid is shown to allow high-resoln. (~100 mm) accurate images to be obtained. Line narrowing is achieved by a combination of magic angle sample spinning (MAS), high-power proton decoupling and deconvolution. The small homogeneous linewidth, high-Q probes and narrow-band receivers assocd. with 13C NMR compensate to a large extent for the low natural abundance and small gyromagnetic ratio of 13C. The resoln. and sensitivity of 13C imaging, which is generally simpler to perform, are comparable to those of multiple pulse 1H imaging. Limitations of the method due to the residual broadening from off-resonance proton decoupling and interference of the MAS averaging of the chem. shift anisotropy by modulated magnetic field gradients are discussed.
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