NMR spin-lattice relaxation

Attard J J, Doran S J, Flerrod N J, Carpenter T A and Flail L D 1992 Quantitative NMR spin-lattice-relaxation imaging of brine in sandstone reservoir cores J. Magn. Reson. 96 514-25... 

Maryott A. A., Farrar T. C., Malmberg M. S. 35C1 and 19F NMR spin-lattice relaxation time measurements and rotational diffusion in liquid CIO3F. J. Chem. Phys. 54, 64-71 (1971). 

C NMR Spin Lattice Relaxation Times (Tj) and Chemical Shifts (6)... 

There has been extensive effort in recent years to use coordinated experimental and simulation studies of polymer melts to better understand the connection between polymer motion and conformational dynamics. Although no experimental method directly measures conformational dynamics, several experimental probes of molecular motion are spatially local or are sensitive to local motions in polymers. Coordinated simulation and experimental studies of local motion in polymers have been conducted for dielectric relaxation,152-158 dynamic neutron scattering,157,159-164 and NMR spin-lattice relaxation.17,152,165-168 A particularly important outcome of these studies is the improved understanding of the relationship between the probed motions of the polymer chains and the underlying conformational dynamics that leads to observed motions. In the following discussion, we will focus on the... 

Another possible solution to the problem of analyzing multiple-layered membrane composites is a newly developed method using NMR spin-lattice relaxation measurements (Glaves 1989). In this method, which allows a wide range of pore sizes to be studied (from less than 1 nm to greater than 10 microns), the moisture content of the composite membrane is controlled so that the fine pores in the membrane film of a two-layered composite are saturated with water, but only a small quantity of adsorbed water is present in the large pores of the support. It has been found that the spin-lattice relaxation decay time of a fluid (such as water) in a pore is shorter than that for the same fluid in the bulk. From the relaxation data the pore volume distribution can be calculated. Thus, the NMR spin-lattice relaxation data of a properly prepared membrane composite sample can be used to derive the pore size distribution that conventional pore structure analysis techniques... 

In order to understand our NMR spin-lattice relaxation experiments we have to revisit some basic features of structural phase transitions. 

In the presence of both order-disorder and displacive, as in the KDP family, the two dynamic concepts have somehow to be merged. It could well be that the damping constant Zs becomes somewhat critical too (at least in the over-damped regime of the soft mode), because of the bihnear coupling of r/ and p. It would, however, lead too far to discuss this here in more detail. The corresponding theory of NMR spin-lattice relaxation for the phase transitions in the KDP family has been worked out by Blinc et al. [19]. Calculation of the spectral density is here based on a collective coordinate representation of the hydrogen bond fluctuations connected with a soft lattice mode. Excellent and comprehensive reviews of the theoretical concepts, as well as of the experimental verifications can be found in [20,21]. 

Variable-temperature 13C NMR spin-lattice relaxation time measurements have been used to probe the motional behavior of 2,3 5,6-di-O-isopropylidene-a-D-mannofuranose (22) in dimethyl sulfoxide solution.67 This carbohydrate deriva-... 

Very recently, Lui and co-workers215 made an attempt to characterise dispersed HPW on mesoporous zeolites silicate-1 and meso-silicate-1, by SS 31P NMR spin-lattice relaxations. They concluded that, on the regular silicalite-1 surface, HPA molecules exist as small agglomerates, while on the mesosilicalite-1 surface about 46% of the HPA molecules are successfully dispersed to the mesoporous channel surfaces. The structural integrity of the surface-exchanged HPA molecules is preserved. Coupled with reaction data, it can be concluded unambiguously that the well-dispersed HPA molecules are the active centres for isomerisation of 1-butene. 

We first discuss the 2H NMR spin-lattice relaxation results of molecular glass formers at T< Tg. In Fig. 53, we present the mean relaxation time (7)), equal to the integral of the corresponding (nonexponential) relaxation function, for several glasses including a polymer (polybutadiene-d6). The temperature-... 

The 1H and 13C NMR spin-lattice relaxation rates in the nickel complex cited earlier in LSR interaction via donor atom were reduced when Gd(fod)3 was added. Gd(III) was found to bind to the two oxygen atoms of the metal complex with Gd(III) ion located... 

NMR spin lattice relaxation measurements provide very direct information about the Fourier transform of the spin susceptibility x( w) in a one-dimensional conductor [39]. The spin degrees of freedom constitute a relaxation channel for nuclear spin due to the modulation of the hyperfine interaction by the electron spin time dependence, which is given generally... 

The 2-site 120° jump motion for the basal molecules switches between these two hydrogen bonding arrangements and clearly requires correlated jumps of the hydroxyl groups of all three basal molecules. On the assumption of Arrhenius behaviour for the temperature dependence of the jump frequencies, the activation energies for the jump motions of the apical and basal deuterons were estimated to be 10 and 21 kj mol-1, respectively. This dynamic model was further supported by analysis of the dependence of the quadrupole echo 2H NMR lineshape on the echo delay and consideration of 2H NMR spin-lattice relaxation time data. 

The temperature dependence of the quadrupole echo 2H NMR lineshape and 2H NMR spin-lattice relaxation time measurements demonstrated that the hydrogen bonding arrangement is dynamic. 

The attractiveness of surface/pore characterization via NMR spin-lattice relaxation measurements of pore fluid lies in the potential advantages this technique has as compared to the conventional approaches. These include rapid analysis, lower operating costs, analysis of wet materials, no pore shape assumption, a wide range of pore sizes can be evaluated (0.5 nm to >1 /im), no network/percolation effects and the technique is non-destructive. When determining specific surface areas, NMR analysis does not require out-gassing and has the potential for on-line analysis of slurries. 

Early studies involving NMR include the work by Hanus and Gill is [6] in which spin-lattice relaxation decay constants were studied as a function of available surface area of colloidal silica suspended in water. Senturia and Robinson [7] and Loren and Robinson [8] used NMR to qualitatively correlate mean pore sizes and observed spin-lattice relaxation times. Schmidt, et. al. [9] have qualitatively measured pore size distributions in sandstones by assuming the value of the surface relaxation time. Brown, et. al. [10] obtained pore size distributions for silica, alumina, and sandstone samples by shifting the T, distribution until the best match was obtained between distributions obtained from porosimetry and NMR. More recently, low field (20 MHz) NMR spin-lattice relaxation measurements were successfully demonstrated by Gallegos and coworkers [11] as a method for quantitatively determining pore size distributions using porous media for which the "actual" pore size distribution is known apriori. Davis and co-workers have modified this approach to rapidly determine specific surface areas [12] of powders and porous solids. 

UC NMR Spin-Lattice Relaxation Times for Starch of Various Origins81... 

Finally, it is interesting whether local relaxation processes of the glassy matrix facilitate ionic diffusion. For phosphate glasses and borate glasses, 31P and nB NMR spin-lattice relaxation studies gave evidence for some coupling of ion and matrix dynamics below Tg. Moreover, it was reported that local rearrange-... 

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