Pulsed gradient spin echo NMR

It is of interest to consider equation (9.4) in the case of two simple examples of motion of importance in this chapter, namely self-diffusion and flow. We write down the result where the motions are superposed. 

The idea that the echo attenuation function could be inverted to yield an image of the average propagator is relatively new and of special value in 

Equation (9.4) is equivalent to the neutron inelastic scattering function for the incoherent fraction. 

This sensitivity to relative motion, (r (t) — i i(0)), makes the interpretation of these methods considerably more difficult, the direct measurement of self- 

The representation of E q) by the average phase shift exp[i27c / ] leads to a useful Taylor expansion 

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O-FID Oxygen-specific flame ionisation PGSE Pulsed gradient spin-echo (NMR)... 

The solvent mobility in atactic polystyrene-toluene solutions has been studied as a function of temperature using NMR. The local reorientation of the solvent was studied using deuterium NMR relaxation times on the deuterated solvent. Longer range motions were also probed using the pulsed-gradient spin-echo NMR method for the measurement of diffusion coefficients on the protonated solvent. The measurements were taken above and below the gel transition temperatures reported by Tan et al. (Macromolecules, 1983. 16, 28). It was found that both the relaxation time measurements and the diffusion coefficients of the solvent varied smoothly through the reported transition temperature. Consequently, it appears that in this system, the solvent dynamics are unaffected by gel formation. This result is similar to that found in other chemically crossed-linked systems. 

Abstract We use Nuclear Magnetic Resonance relaxometry (i.e. the frequency variation of the NMR relaxation rates) of quadrupolar nucleus ( Na) and H Pulsed Gradient Spin Echo NMR to determine the mobility of the counterions and the water molecules within aqueous dispersions of clays. The local ordering of isotropic dilute clay dispersions is investigated by NMR relaxometry. In contrast, the NMR spectra of the quadrupolar nucleus and the anisotropy of the water self-diffusion tensor clearly exhibit the occurrence of nematic ordering in dense aqueous dispersions. Multi-scale numerical models exploiting molecular orbital quantum calculations, Grand Canonical Monte Carlo simulations, Molecular and Brownian Dynamics are used to interpret the measured water mobility and the ionic quadrupolar relaxation measurements. 

A Multiscale Analysis of 1H Pulsed Gradient Spin-Echo NMR Measurements. 

Diffusion coefficients derived from pulsed gradient spin echo NMR-studies show lower values for the encapsulated guest identical to those of the host, see Frish, L. Matthews, S. E. Bohmer, V. Cohen, Y. J. Chem. Soc., Perkin Trans. 2 1999, 669-671. 

Figure 5.1 Pulsed-gradient spin-echo NMR sequence for the measurement of self-diffusion coefficient.

Fig. 1. Gradient of rf sequence for pulsed gradient spin-echo NMR using narrow gradient pulses of amplitude g, duration 8, and separation A.

Callaghan, P. T. (1995). Pulsed gradient spin echo NMR for planar, cylindrical and spherical pores under condition of wall relaxation. J. Magn. Reson. (in press). 

Callaghan, P. T., and Stepisnik, J. (1995b). Spatially-distributed pulsed gradient spin echo NMR using single-wire proximity. Phys. Rev. Lett. 75, 4532-4535. 

Diffusion of Water in poly[PFSA] Membranes To describe diffusion of water through the membrane in the presence of a water activity gradient, an appropriate interdiffusion coefficient must be determined. Experimental methods used to study diffusion of water in these polymers, such as radiotracer and pulsed gradient spin-echo NMR techniques, probe intrad-iffusion coefficients, often referred to as tracer or self-diffusion coefficients, determined in the absence of a chemical potential gradient. Intra- and interdiffusion coefficients are related for the case of diffusion of a small molecule in a polymeric matrix as follows [28] ... 

Zhu XX, MacDonald PM, Pulsed-gradient spin-echo NMR measurements of the diffusion coefficients of ketones in poly(methyf methacrylate). Maeromolecules 1992 25, 4345. 

PGSENMR Pulsed gradient spin echo NMR for self-diffusion measurements... 

Belfort and Segvers (unpublished results) have seen for adsorbed water in 24 A diameter porous glass, reductions in the measured (by pulsed gradient spin echo NMR) water self-diffusion... 

The solubility of hydrocarbons in water is greatly enhanced by the presence of surfactants. Similarly, the addition of hydrocarbons to aqueous surfactant solution induces change in the physical properties of the surfactant (24, 25). Thus, the quantitative analysis of the partitioning of hydrocarbons between micelle interior and aqueous phase has been a subject of numerous studies. Among the many techniques used to determine the partitioning, only fluorescence (26), FT-pulsed-gradient spin echo NMR (27), and recently, Raman spectroscopy (28) have demonstrated sufficient sensitivity. 

Figure 7.1.4 shows the effect of concentration of polystyrene on mutual and self-diffusion coefficients measured by pulsed-gradient spin-echo NMR. The data show that the two coefficients approach each other at high concentrations of polymer as predicted by theory. ... 

Pulsed gradient spin echo NMR was used to measure the diffusion coefficients of hydrophobically modified alkali-swellable (HASH) associating polymers (AP) in aqueous solution. The HASH APs consisted of a methacrylic acid-ethyl acrylate copolymer to which hydrophobic sticker ... 

R. Nanda, P.R. Rajamohanan, A. Kumar, Experimental signature of microheterogeneity in ionic hquid-H20 systems and their perturbation by adding Li salts a pulsed gradient spin-echo NMR approach, ChemPhysChem 16 (14) (2015) 2936—2941. Ahead of Print. 

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