Field gradient spin methods

We finish this section by comparing our results with NMR and incoherent neutron scattering experiments on water dynamics. Self-diffusion constants on the millisecond time scale have been measured by NMR with the pulsed field gradient spin echo (PFGSE) method. Applying this technique to oriented egg phosphatidylcholine bilayers, Wassail [68] demonstrated that the water motion was highly anisotropic, with diffusion in the plane of the bilayers hundreds of times greater than out of the plane. The anisotropy of... 

Meerwall v., E. D. Self-Diffusion in Polymer Systems. Measured with Field-Gradient Spin Echo NMR Methods, Vol. 54, pp. 1—29. 

Field gradient spin echo method of measuring self-diffusion, encompasses SGSE and PGSE variants. 

In polymers, the field-gradient spin-echo methods of measuring self-diffusion have been useful in three more or less distinct areas, the diffusion of polymers in their own melt and in concentrated solutions, in dilute and semidilute solutions, and the diffusion of penetrants and diluents in polymer hosts. A fourth category, the diffusion of bulky or flexible molecules in polymer hosts, is useful for subject matter not closely associated with the first and third category. It should be noted that the work reviewed here represents only a small fraction of the diffusion studies in polymers, including those using other NMR methods. 

The field gradient spin echo methods appear now to have amply proven their validity and usefulness in the study of polymer systems. This early work has been understandably academic in flavor, but there seems to be no impediment to the use of FGSE measurements for routine rheological characterization, e.g., to... 

Self-Diffusion in Polymer Systems, Measured with Field-Gradient Spin-Echo NMR Methods... 

By the pulsed field gradient spin echo method (1) it is possible to measure mean diffusion lengths ( /(l2)) for molecules in a given time interval in systems without a concentration gradient. The application of the method is limited to... 

Figure 4 Methods of selectivity enhancement using pulsed field gradients employing (a) selective excitation pulses, (b) a selective refocusing pulse and (c) a double piUsed field gradient spin echo (DPFGSE) sequence with inversion pulses...

Other indications about the intramolecular reaction were concluded from pulsed field gradient spin echo-NMR (PGSE-NMR) measurements [60]. This method gives informations about the incorporation of the substrate into the micelle and enabled the measurement of an average diffusion coefficient of the catalyst below and above the CMC. 

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