NMR diffusion measurements of strong signals: The PGSE-Q-switch experiment

NMR diffusion measurements of samples with strong resonances are particularly problematic owing to the effects of radiation damping and become even more difficult at higher static fields and with more sensitive probes. Here, a new PGSE sequence incorporating Q-switching that totally removes the effects of radiation damping is presented. The sequence affords the possibility of performing diffusion measurements of concentrated samples at normal sample volumes at high field, and thus has particular relevance for gradient calibration, diffusive diffraction and LC-NMR experiments. Further, because the relaxation behaviour of all of the species is unaffected by radiation damping, the incorporation of sophisticated sequence elements is facilitated and data analysis is simplified. The new sequence is demonstrated on a sample containing 90% water and 1% ethanol.