15-T, 4.2-K FIELD-SWEPT AL-27 NMR-SPECTROSCOPY

A field-swept NMR spectrometer has been constructed based on a 16 T (4.2 K operation) superconducting magnet, the largest magnetic field yet used for field-swept NMR. We find that the experiment is relatively easy to perform for Al-27 NMR and the spectra of alpha-Al2O3 are of high quality. There are two important advantages that we discuss herein: (1) resonances with exceedingly wide line widths can be studied and (2) operation at 4.2 K largely eliminates proton hopping and the resulting motional averaging of the electric field gradient at the aluminum sites.