High-resolution multiple quantum MAS NMR spectroscopy of half-integer quadrupolar nuclei

We demonstrate the utility of a two-pulse sequence in obtaining high-resolution solid state NMR spectra of half-integer quadrupolar nuclei with magic angle-spinning (MAS). The experiment, which utilizes multiple/single-quantum correlation, was first described in a different form by Frydman and Harwood [J. Am. Chem. Sec. 117 (1995) 5367] and yields high-resolution isotropic NMR spectra where shifts are determined by the sum of resonance offset (chemical shift) and second-order quadrupolar effects, The two-pulse sequence described here is shown to provide a higher and more uniform excitation of multiple-quantum coherence than the three-pulse sequence used previously.