Title: Pulsed field gradient stimulated echo methods for improved NMR diffusion measurements in heterogeneous systems
Abstract: The NMR pulsed magnetic field gradient stimulated echo technique of Tanner is especially useful for measuring the translational diffusion coefficient, D, of the resonant nucleus in materials where T1 ⪢ T2. However, in heterogeneous systems having components with dissimilar magnetic susceptibilities, a distribution of background gradients, g0, may cause excessive signal (echo) attenuation and a systematic error in the measurement of D. Three new stimulated echo sequences involving applied field gradient pulses, of amplitude ga, together with RF pulses, are described. For all of these sequences the echo attenuation and systematic error caused by g0 and g0ga terms, respectively, are greatly reduced. For one of the sequences, this reduction can be realized with gradient pulses of a single polarity. With bipolar (alternating) gradient pulses the cross term can be made to vanish, with the correct choice of conditions, for all three of the sequences. Two of the new sequences have been tested experimentally by means of D measurements involving 1H signals in bulk glycerol (homogeneous) and in granular TaH0.73 (heterogeneous) samples.
Publication Year: 1989
Publication Date: 1989-06-01
Language: en
Type: article
Indexed In: ['crossref']
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Cited By Count: 677
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