Steady state effects in PGSE NMR diffusion experiments

The consequences of performing the Hahn spin-echo based PGSE sequence in steady state mode are investigated. Theory suggests that addition of a crusher gradient pulse during the prescan delay should result in a steady state of magnetisation at the beginning of each instance of the pulse sequence regardless of the length of the recycle delay. Although theoretical analysis reveals that substantially shorter recycle delays can be used, experiments reveal that very short recycle delays result in significant deviation in the measured diffusion coefficient as determined by a standard PGSE experiment with a recycle delay sufficient for full thermal relaxation (normally ∼5 × T1).