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 studied^1-7. 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' approach^4,7. 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).