Diffusion measurements using radiofrequency field gradient: artifacts, remedies, practical hints

ABSTRACT

The two major advantages of experiments carried out with radiofrequency (RF) field-gradient NMR are the instrumental simplicity and the insensitivity to background static magnetic field gradients. These features combined with large RF gradients, which became available only recently, should make this technique especially attractive for molecular translational diffusion studies. However, a critical evaluation of the method shows that under some circumstances (small and/or heterogeneous samples, weak diffusion coefficients, very short relaxation times) the quality of measurements may be affected by a number of artifacts. Their origin has been investigated and several remedies have been considered; in particular, a new improved sequence is presented. The success of various experimental tests demonstrates the efficiency of the proposed solutions which thus open the way to much wider application fields. Copyright 1998 Academic Press.