Experimental Capability Of High Resolution O17 Using Double Rotation On Crystalline Sodium Enneagermanate

Abstract

We have studied sodium enneagermanate crystal using both magic angle spinning (MAS) and double rotation (DOR) at two magnetic field strengths. Using equation for the total shift observed at two field strengths, the chemical shift is uniquely determined together with a product of the quadrupolar coupling constant (CQ = e2qQ/h) and the quadrupolar asymmetry parameter (ç). We demonstrate a computer simulation that uses the isotropic shifts and quadrupolar products as constraints and provides simulations of overlapped magic-angle spinning line shapes. In this way the quadrupolar parameters, CQ and ç, are determined separately for each crystallographic site of crystalline sodium enneagermanate. High resolution DOR spectra of oxygen-17 nuclei in sodium enneagermanate crystal illustrate the experimental capabilities. Crystalline studies of sodium enneagermanate is one of the structural data for confirming the correlations between the measured 17O quadrupolar coupling parameters and the oxygen environment. The result of these studies should provide insight to further investigation using 17O solid state NMR to study the structure of other oxide glasses and as well as other germanate-based glasses.