Identification of a defect chain motion inn‐alkanes by means of nuclear magnetic resonance spin–lattice relaxation time measurements

1990 ◽  
Vol 93 (5) ◽  
pp. 3604-3609 ◽  
Author(s):  
Ilsa Basson ◽  
Eduard C. Reynhardt
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Relaxation Time ◽  
Magnetic Resonance ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Spin Lattice Relaxation Time ◽  
Spin Lattice ◽  
Resonance Spin ◽  
Nuclear Magnetic

A nuclear magnetic resonance investigation of solid cyclo hexane

1953 ◽  
Vol 216 (1126) ◽  
pp. 398-412 ◽  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Relaxation Time ◽  
Magnetic Resonance ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Second Moment ◽  
Bond Lengths ◽  
Spin Lattice Relaxation Time ◽  
Spin Lattice

The nuclear magnetic resonance absorption spectrum and the spin-lattice relaxation time have been measured for the protons in polycrystalline cyclo hexane between 100° K and its freezing-point (279·6° K). It has been found that the second moment (mean square width) of the measured spectrum for temperatures at which the lattice is effectively rigid, namely, below 150° K, is consistent with a molecular structure having D 3d symmetry, tetrahedral bond angles, C—C bond lengths of 1.54 Å and C—H bond lengths of 1.10 A. If the HCH angle is treated as a parameter to be determined, it is found to be 1071/2 ± 3°. On warming from 155 to 180° K the second moment decreases to a value which indicates the reorientation of the molecules about their triad axes. Analysis of the spin-lattice relaxation time, which falls rapidly in this temperature range, shows that the height of the barrier hindering this reorientation is 11 ± 1 kcal/mole. Just below 186° K, the temperature at which there is a polymorphic change, the reorientation frequency is of the order 10 6 c/s. The polymorphic transformation is accompanied by discontinuous changes in the second moment and the relaxation time. It is concluded that in the higher temperature modification the molecules have a considerable freedom of reorientation, such that the intramolecular contribution to the second moment becomes negligibly small. Just above 186° K the mean reorientation frequency exceeds 3 x 10 7 c/s. A final narrowing of the line between 220 and 240° K is thought to be due to vacancy diffusion of the molecules within the lattice, causing the intermolecular contribution to the second moment to vanish also. Details are given of the gas-flow cryostat used in this work. The theoretical formulation of the second moment has been extended to include the modification of the intermolecular contribution during reorientation.

scholarly journals Imaging of nuclear magnetic resonance spin–lattice relaxation activation energy in cartilage

2018 ◽  
Vol 5 (7) ◽  
pp. 180221 ◽  
Author(s):  
R. J. Foster ◽  
R. A. Damion ◽  
M. E. Ries ◽  
S. W. Smye ◽  
D. G. McGonagle ◽  
...  
Keyword(s):  
Activation Energy ◽  
Nuclear Magnetic Resonance ◽  
Relaxation Time ◽  
Magnetic Resonance ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Cartilage Tissue ◽  
Spin Lattice ◽  
Resonance Spin ◽  
Nuclear Magnetic

Samples of human and bovine cartilage have been examined using magnetic resonance imaging to determine the proton nuclear magnetic resonance spin–lattice relaxation time, T 1 , as a function of depth within through the cartilage tissue. T 1 was measured at five to seven temperatures between 8 and 38°C. From this, it is shown that the T 1 relaxation time is well described by Arrhenius-type behaviour and the activation energy of the relaxation process is quantified. The activation energy within the cartilage is approximately 11 ± 2 kJ mol −1 with this notably being less than that for both pure water (16.6 ± 0.4 kJ mol −1 ) and the phosphate-buffered solution in which the cartilage was immersed (14.7 ± 1.0 kJ mol −1 ). It is shown that this activation energy increases as a function of depth in the cartilage. It is known that cartilage composition varies with depth, and hence, these results have been interpreted in terms of the structure within the cartilage tissue and the association of the water with the macromolecular constituents of the cartilage.

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