Optimized multiple-quantum magic-angle spinning NMR experiments on half-integer quadrupoles

It has been recently shown that second-order anisotropies can be removed from solid phase NMR spectra of quadrupolar nuclei via the combined use of magic-angle spinning (MAS) and bidimensional multiple-quantum (MQ) spectroscopy. The present study investigates the conditions under which the acquisition of such high-resolution MQMAS NMR spectra are optimized. The excitation and conversion pulse lengths that maximize 0 → ±3(t1) → − 1 (t)2) coherence transfer pathway signals for arbitrary spin numbers were calculated, as were the pulse lengths that provide NMR spectra free from dispersive line shape distortions. For the case of spin-5/2 nuclei, the conditions which optimize experiments involving quintuplequantum coherences were also determined.