High-resolution solid-state NMR of quadrupolar nuclei

Quadrupolar nuclei are the most abundant nuclear magnetic resonance (NMR)-receptive nuclei in the Earth's crust, and in many amorphous materials of technological interest (such as zeolite catalysts, ceramics and alloys), and have thus been intensively studied1–7. Of particular interest is the ability to resolve and quantitate the various types of sites present in a given material. Here we present a very simple, yet we believe powerful, approach towards the resolution of chemically non-equivalent sites in solids, which combines a conventional high-field spin-echo NMR method with the resolution enhancement of the ‘quadrupole shift’ approach4,7. We demonstrate its application to the complete resol-ution of both the (1/2, 3/2) and (3/2, 5/2) transitions of the 27Al nuclei in a mixture of potassium and ammonium alums (KAl(SO4)2·12H2O and NH4Al(SO4)2·12H2O).

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