NMR diffusion measurements in heterogeneous media using pulsed radio-frequency field gradients

The measurement of self-diffusion coefficients D by the NMR spin echo pulsed-field gradient G technique can be corrupted for systems having a background magnetic field gradient G(o). The corrupting cross-term G(o)G can be eliminated by the use of alternating pulsed-field gradient sequences. Measurement of D can also be performed by a rather new technique using pulsed radio-frequency field gradients and rotary echoes. This technique is basically insensitive to background gradients and does not generate any adverse effects such as eddy currents or sample vibration. These methods have been applied to mesoporous solids and heteropolyacids. (C) 1998 Elsevier Science B.V. All rights reserved