Nuclear magnetic relaxation principles

Norbornyl cation reappraisal of structure, 11, 179 Nuclear magnetic relaxation, recent problems and progress, 16, 239 Nuclear magnetic resonance see NMR Nuclear motion, principle of least, 15, 1... 

A complementary article by Dais (Iraklion, Crete) addresses the theoretical principles underlying the phenomenon of carbon-13 nuclear magnetic relaxation, encompassing spin-lattice (Tt) and spin-spin (T2) relaxation times, the nuclear Overhauser enhancement, and their relation to the motional behavior of carbohydrates in solution. With examples broadly selected from simple sugar derivatives, oligosaccharides, and polysaccharides, the author shows how qualitative treatments have provided useful interpretations of the gross mobility of molecules in solution, but demonstrates how a quantitative approach may be of greater ultimate value. 

F. Noack, "Nuclear magnetic relaxation spectroscopy" in NMR, Basic Principles and Progress, vol. 3, edited by P. Diehl, E. Fluck, and R. Kosfeld (Springer Verlag, Berlin, 1971), pp. 83-144. 

As we shall see, all relaxation rates are expressed as linear combinations of spectral densities. We shall retain the two relaxation mechanisms which are involved in the present study the dipolar interaction and the so-called chemical shift anisotropy (csa) which can be important for carbon-13 relaxation. We shall disregard all other mechanisms because it is very likely that they will not affect carbon-13 relaxation. Let us denote by 1 the inverse of Tt. Rt governs the recovery of the longitudinal component of polarization, Iz, and, of course, the usual nuclear magnetization which is simply the nuclear polarization times the gyromagnetic constant A. The relevant evolution equation is one of the famous Bloch equations,1 valid, in principle, for a single spin but which, in many cases, can be used as a first approximation. 

Lipari G. and Szabo A. (1980) Effect of Vibrational Motion on Fluorescence Depolarization and Nuclear Magnetic Resonance Relaxation in Macromolecules and Membranes, Biophys. J. 30, 489—506. Steiner R. F. (1991) Fluorescence Anisotropy Theory and Applications, in Lakowicz J. R. (Ed.), Topics in Fluorescence Spectroscopy, Vol. 2, Principles, Plenum Press, New York, pp. 127-176. 

Moreover, we note that recently in reconstructing relaxation times via the time-temperature superposition principle using double quantum nuclear magnetic resonance (DQ-NMR) the and power laws were invoked without giving the spatial information of NSE [75]. 

H. Pfeifer, Nuclear Magnetic Resonance and Relaxation of Molecules Adsorbed on Solids in NMR - Basic Principles and Progress, Springer, Berlin, 7 (1972) pp. 105-115. 

The information content of nuclear longitudinal relaxation measurements in both paramagnetic and diamagnetic systems can be greatly increased by performing such measurements as a function of the magnetic field. For paramagnetic species, the reason is apparent from the functional form of the equations discussed in Chapter 3 and from the relevant experimental data, reported in Chapter 5. The field dependence of a relaxation rate is called relaxation dispersion, and is abbreviated as NMRD. In principle, NMRD would be helpful for any chemical system, but practical limitations, as will be shown, restrict its use, with a few exceptions, to water protons. 

A nuclear magnetic resonance spin-lattice relaxation technique was recently successfully demonstrated on a number of types of porous media. The basic principle is that the portion of pore fluid near a pore wall undergoes spin-lattice relaxation in a magnetic field faster than pore fluid removed from the pore wall [45]. 

This phenomenon of super-radiance is used in the photon-echo technique for high-resolution spectroscopy to measure population and phase decay times, expressed by the longitudinal and transverse relaxation times Ti and T2, see (7.1). This technique is analogous to the spin-echo method in nuclear magnetic resonance (NMR) [904]. Its basic principle may be understood in a simple model, transferred from NMR to the optical region [905]. 

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