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NMR studies of clustering in solids.

The authors present a time-resolved multiple-quantum NMR experiment which allows us to determine the spatial distribution of atoms in materials lacking long-range order; in particular, they study the size and extent of atomic clustering in these materials. Multiple-quantum NMR is sensitive to the distribution of spins in a solid. At the two extremes, uniformly distributed spins absorb radio-frequency quanta continuously, whereas clustered groups of N spins can absorb only up to N quanta. Model experiments are demonstrated on the hydrogen distribution in selectively deuterated organic solids and in hydrogenated amorphous silicon.