Journal of Magnetic Resonance (1969)
A modified pulsed gradient technique for measuring diffusion in the presence of large background gradients☆
Abstract
An NMR technique for measuring the diffusion constant D in the presence of a large nonuniform background magnetic field gradient G0 is presented. The technique uses a Carr-Purcell-Meiboom-Gill of pulse train that attenuates the effects of diffusion due to the background gradient, interspersed with an alternating pulsed field gradient sequence (APFG) that attenuates the observed echo in the presence of the known applied gradient. Calculations for the observed echo amplitude are presented that show the APFG technique eliminates contributions from the cross term between the background and applied gradients. Results of tests of the technique are presented for the measurement of D in H2O in the presence of G0 ∼ 160 G/cm. Also described are the results of preliminary measurements of D in LaNi5H6; D = (6.2 ± 0.5) × 10−8 cm2/see at 331.2 K and G0 ∼ 2.9 kG/cm.
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This work supported by NSF Grant DMR 76-22655.
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Supported in part by Energy Research Development Administration.