Multiple-quantum nuclear magnetic resonance spectroscopy of coupled 1/2 spins in solids. Combination with cross-polarization and magic-angle spinning.
Proton multiple-quantum coherence spectroscopy was combined with magic-angle spinning (MAS) and cross-polarization (CP). This enables the detection of the proton (or any other abundant spin) multiple-quantum coherence spectrum via the high-resoln. 13C (any other spin) NMR spectrum. For this purpose multiple-quantum pulse sequences synchronized to sample rotation were designed, and the av. Hamiltonians of these sequences were analyzed. The anal. allows the design of optimal exptl. conditions. As a demonstration of the technique, it was applied to a mixt. of adamantane and hexamethylethane. From earlier 13C spin diffusion expts. these two mols. form a mixed crystal. With the technique the authors detected two different phases with different mol. translational self-diffusion coeffs. in this system.
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