Spin lattice time measurement

Canet D, Levy G C and Peat I R 1975 Time saving in C spin-lattice relaxation measurements by inversion-recovery J. Magn. Reson. 18 199-204... 

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... 

Spin-lattice relaxation measurements (7j) are also common,78 83 though these of course monitor more rapid motions. Spin lattice relaxation times have nevertheless proved a simple but effective means of distinguishing different structural regions within polymer samples, i.e. crystalline and amorphous regions and interfacial regions between crystalline and amorphous parts. 

Complementary spin-lattice relaxation measurements corroborate the observations made using the 2H line-shape measurements. Based on these measurements the low temperature relaxation times are dramatically shorter in the intercalated sample as compared to the bulk, indicating enhanced polymer re-orientation dynamics in the intercalated samples. Furthermore, the temperature dependence of the relaxation time in the bulk and intercalated sample show dramatic differences. While the relaxation time for the intercalated sample passes smoothly from low to high temperatures, the bulk sample shows a break between the crystalline state and melt state, with the melt state relaxation times at least one order of magnitude faster than those observed in the intercalated sample at the same temperature. 

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... 

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. 

Two further studies, one by Villafranca and Viola,309 who carried out 13C spin-lattice relaxation measurements on the interaction of methyl a-D-glucopyranoside with con A, and the other by Alter and Mag-nuson,310 who characterized the binding of 2-deoxy-2-(trifluoroacetamido)-D-glucose to the lectin, placed the saccharide at 1.0 to 1.4 nm from the Mn2+ion, in agreement with the results of Brewer and coworkers.307,308 Villafranca and Viola s model309 placed C-l, C-2, and C-6 closest to the Mn2+ (see Fig. 3). On the other hand, support for the cavity proposed by Becker and coworkers280 comes from p.m.r.-spectral measurements of the longitudinal relaxation-times of the methyl proton of methyl a-D-mannopyranoside with Zn2+- and Gd2+-substituted con A.311,312... 

D. Canet, G. C. Levy, and I. R. Peat, "Time saving in 13C spin-lattice relaxation measurements by inversion recovery," J. Magn. Resonance 18, 199-204 (1975). 

The relaxation dynamics of junctions in polymer networks have not been well known until the advent of solid-state P NMR spin-lattice relaxation measurements in a series of poly(tetrahydrofuran) networks with tris(4-isocyanatophenyl)-thiophosphate junctions (Shi et al., 1993). The junction relaxation properties were studied in networks with molecular weights between crosslinks, Me, ranging from 250 to 2900. The dominant mechanism for P nuclear spin lattice relaxation times measured over a wide range of temperatures were fit satisfactorily by spectral density functions, 7([Pg.225]

Fig. 2.27 (a) Spin-lattice time Ti, (b) phase memory time Tm, and (c) field sweep pulsed ESR measured at room temperature on an X-irradiated K2S2O6 polycrystaUine sample, (a) Ti measurement was performed using an inversion recovery pulse sequence, (b) Tm measurement was performed using a Hahn echo sequence, (c) The pulsed ESR spectrum was obtained by measuring the Hahn echo intensity as a function of the magnetic field. The data were provided by Dr. H. Gustafsson... 

Measurements of coupling constants and C spin lattice times for C-enriched tetroses and tetrofuranosides have enabled conformational changes and ring dynamics to be determined a thorough... 

Han et al. studied the dynamics of hydrated water molecules in NAFION by means of high-resolution MAS NMR measurements. Bound and free states of hydrated water clusters as well as the exchange protons were identified from the NMR chemical shift measurements, and their activation energies were obtained from the temperature-dependent laboratory- and rotating-frame spin-lattice relaxation measurements. Besides, a pecufiar motional transition in the ultralow frequency region was observed at 373 K for the free hydrated water from the rotating-frame NMR spin-lattice relaxation time measurements [60]. 

Spin-lattice and spin-spin relaxation times measured by the saturation method at X-band ESR for the PANI-PTSA with y = 0.5 are Tj = 1.1 x 10 s and T2 = 1.6 x 10 s. For polarons, diffusion along and between polymer chains in this highly doped polymer, = 8.1 x 10 rad s and = 2.3 x 10 rad s , should be evaluated from Eqs. 10. The value Oid/Dsd = 10 substantially exceeds the value D1D/D3D 50 obtained for highly doped PANI-HCA. The corresponding terms of conductivity due... 

Three papers have dealt with NMR relaxation of small organic molecules dissolved in organic solvents. Kathmann et al. reported and spin-lattice relaxation measurements for cyclic amines (pyridine, 2,6-lutidine, 2,2,6,6-tertamethyl piperidine) in toluene and dichloromethane solutions. The rotational correlation times were derived from NMR data and compared with MD simulations. Alemany discussed highly resolved spectra for long-chain n-alkanes with 12-22 carbons, dissolved in benzene or toluene. Besides the chemical shifts, also the Ti data were obtained and related to segmental motions. Ekinci and co-workers studied Ti data for the chiral iV-benzil-2-isobutyl aza-15-crown-5-ether derivative as a function of temperature. The rotational correlation times and their activation energy were derived. 

Solution 13C spin-lattice relaxation measurements were performed on instruments operating at 11.75 and 7.05 Tesla. Experiments were conducted at five different temperatures (283 K, 293 K, 303 K, 313 K, and 323 K). Temperature accuracy for these measurements is +0.1 K. Relaxation times were obtained using the standard inversion-recovery pulse sequence as described in our earlier work [1-5]. Relaxation times in the various solvents are shown in Tables 2, 3, and 4. 

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