Multiple-quantum pulsed gradient NMR diffusion experiments on quadrupolar (I > 12) spins

The implementation of the multiple-quantum (MQ) versions of the PGSE and LED pulsed field-gradient NMR diffusion experiments is described for the coherence order 2I for isolated quadrupolar (spin I) nuclei in anisotropic systems. The MQPGSE and MQLED experiments are capable of measuring slow diffusion accurately, the latter also in the case of fast transverse relaxation. Signal-to-noise ratios are discussed, and the methods are experimentally demonstrated for 7Li+ (I = 32) in an oriented sample of DNA fibers.