Nuclear magnetic resonance spectrum relaxation

Aksnes, D.W., Hutchison, S.M. and Packer, K.J. (1968) Nuclear spin relaxation and chemical exchange effects in the 19F nuclear magnetic resonance spectrum of the hexafluoroniobate ion. Mol. Phys., 14, 301-309. 

Nuclear spin relaxation measurements were made of single crystals at between 150 and 1500K, under an O partial pressure of latm. The nuclear magnetic resonance spectrum consisted of a doublet which resulted from 2 different orientations of the electric field gradient tensor at 2 different Ti sites in the unit cell of the rutile lattice. The electric field gradient tensor was due to the 6 surrounding q2- ions, which formed a stretched octahedron. From the temporal evolution of the nuclear spin relaxation rate after a step-wise change in the 0 partial pressure, 2 different types of motion of the intrinsic defects were... 

Whereas the paramagnetic shift of the nuclear magnetic resonance frequency for a given applied field is related to the strength of the local hyperfine field at the nuclear site, induced by the electronic moments, the nuclear spin-lattice relaxation rate yields information about the low-frequency spectrum of thermally induced spin fluctuations. The influence of pair-correlation effects on the NMR relaxation in paramagnets was analysed experimentally and theoretically by... 

Nuclear magnetic resonance (NMR) spectroscopy has great relevance in the area of investigation of molecular structures. Many studies using NMR spectroscopy and microscopy have been reported in elastomer based systems. Due to the possibihty of reuse of samples after the analysis (NMR is nondestructive) NMR attracts many material scientists to select this technique for characterization. In the case of polymers NMR is specifically useful in finding out the crosslink density. Since the crosslink density is related to the size of pores or cavities inside solid polymers, this method points towards the structural elucidation of polymers. From the parameters such as magnetic relaxation and the dipolar correlation effect obtained from the NMR spectrum, crosslink density can be calculated. In addition to the crosslink density, the behaviour of small particles inside the polymer matrices can also be... 

Another interesting spectroscopy performed on SmBg is nuclear magnetic resonance (NMR) where the temperature dependence of the B relaxation rate has been measured by Pena et al. (1981). Above 10 K the temperature dependence is exponential with a gap of 5.6 meV The authors interpret their results as the consequence of the fluctuations of 4f spins thus relating the measured line width to the contribution of the hyperfine field from these fluctuations. The NMR experiments thus measure directly a gap in the 4f spectrum, where the only other experiment, directly related to a gap in the 4f spectrum, was the IDS obtained by optical reflection by Travaglini and Wachter (1984a). Similar NMR results have been obtained by Takigawa et al. (1983). 

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