Spin–lattice relaxation

About: Spin–lattice relaxation is a research topic. Over the lifetime, 8133 publications have been published within this topic receiving 155446 citations.

Model-free approach to the interpretation of nuclear magnetic resonance relaxation in macromolecules. 1. Theory and range of validity

Abstract: A new approach to the interpretation of nuclear magnetic resonance relaxation experiments on macromolecules in solution is presented. This paper deals with the theoretical foundations and establishes the range of validity of this approach, and the accompanying paper demonstrates how a wide variety of experimental relaxation data can be successfully analyzed by using this approach. For both isotropic and anisotropic overall motion, it is shown that the unique imformation on fast internal motions contained in relaxation experiments can be completely specified by two model-independent quantities; (1) a generalized order parameter, S, which is a measure of the spatial restriction of the motion, and (2) an effective correlation time, T/sub e/, which is a measure of the rate of motion. A simple expression for the spectral density involving these two parameters is derived and is shown to be exact when the internal (but not overall) motions are in the extreme narrowing limit. The model-free approach (so called because S/sup 2/ and T/sub e/ have model-independent significance) consists of using the above spectral density to least-squares fit relaxation data by treating S/sup 2/ and T/sub e/ as adjustable parameters. The range of validity of this approach is illustrated by analyzing error-free relaxationmore » data generated by using sophisticated dynamical models. Empirical rules are presented that allow one to estimate the of S/sup 2/ and T/sub e/ extracted by using the model-free approach by considering their numerical values, the resonance frequencies, and the parameters for the overall motion. For fast internal motions, it is unnecessary to use approaches based on complicated spectral densities derived within the framework of a model because all models that can give the correct value of S/sup 2/ work equally well.« less

Theory of the Effect of Spin-Orbit Coupling on Magnetic Resonance in Some Semiconductors

Abstract: The effect of spin-orbit coupling on the usual band theory of electrons in a lattice is considered. Particular attention is given to the bands in impurity semiconductors with diamond-type structure. $g$-values are calculated for electron states typical of various possible cases and it is found that different values are obtained according as to whether the Fermi level is near or distant from a band degeneracy. The spin-lattice relaxation time is calculated so that the effect of spin-orbit coupling on the wave functions is included, and times in fair agreement with those observed in silicon and alkali metals are obtained.

T1, T2 relaxation and magnetization transfer in tissue at 3T

Abstract: T1, T2, and magnetization transfer (MT) measurements were performed in vitro at 3 T and 37 degrees C on a variety of tissues: mouse liver, muscle, and heart; rat spinal cord and kidney; bovine optic nerve, cartilage, and white and gray matter; and human blood. The MR parameters were compared to those at 1.5 T. As expected, the T2 relaxation time constants and quantitative MT parameters (MT exchange rate, R, macromolecular pool fraction, M0B, and macromolecular T2 relaxation time, T2B) at 3 T were similar to those at 1.5 T. The T1 relaxation time values, however, for all measured tissues increased significantly with field strength. Consequently, the phenomenological MT parameter, magnetization transfer ratio, MTR, was lower by approximately 2 to 10%. Collectively, these results provide a useful reference for optimization of pulse sequence parameters for MRI at 3 T.