Theory Of Nuclear Magnetic Relaxation Research Articles

QUADRELAX: A Program for Computing Relaxation Data for Quadrupolar Nuclei, Including Chemical Exchange Effects

Based on Redfield's theory of nuclear magnetic relaxation, a computer package capable of computing longitudinal and transverse relaxation rates and amplitudes as well as dynamic frequency shift for all quadrupolar nuclei (all integer spin numbers from 1 to 6 and all half‐integer spin numbers from to ) in all molecular movement regimes including the effects of two‐site chemical exchange was introduced. As an example, the calculated longitudinal and transverse relaxation rates for spin nuclei were plotted versus which had not been reported previously. These diagrams show the possibility of the usage of the central transition in the NMR of biomolecules containing spin nuclei. The data produced by this package can be used for simulating the NMR spectra of quadrupolar nuclei, involving in exchange processes, which can be used to extract kinetic data from NMR spectra. The accuracy of this package was confirmed using it for reproducing of the data in some problems investigated earlier. Our data are in full accordance with the conducted research in this area. © 2015 Wiley Periodicals, Inc. Concepts Magn Reson Part A 43A: 228–236, 2015.

Modified Spin-Wave Theory of Nuclear Magnetic Relaxation in One-Dimensional Quantum Ferrimagnets: Three-Magnon versus Raman Processes

Nuclear spin-lattice relaxation in one-dimensional Heisenberg ferrimagnets is studied by means of a modified spin-wave theory. Calculating beyond the first-order mechanism, where a nuclear spin directly interacts with spin waves through the hyperfine coupling, we demonstrate that the exchange-scattering-enhanced three-magnon nuclear relaxation may generally predominate over the Raman one with increasing temperature and decreasing field. Recent proton spin-lattice relaxation-time (T_1_) measurements on the ferrimagnetic chain compound NiCu(C_7_H_6_N_2_O_6_)(H_2_O)_3_2H_2_O suggest that the major contribution to 1/T_1_ be made by the three-magnon scattering.

Theory of nuclear magnetic relaxation in Haldane-gap antiferromagnets.

A theory of nuclear magnetic resonance is developed for integer-spin, one-dimensional antiferromagnets, which exhibit the Haldane gap. We consider free boson, free fermion, and nonlinear $\ensuremath{\sigma}$-model approaches, all of which give similar results. The detailed anisotropy and magnetic field dependence is calculated and compared with experiment.

Theory of nuclear magnetic relaxation in the doped high critical temperature superconductor; a marginal - Fermi - liquid approach

We calculated the nuclear magnetic relaxation rate T 1 for the normal phase of a doped high temperature superconductor described by the generalised marginal Fermi liquid. The deviations from the marginality introduced by the scaling hypothesis in order to explain the non - linear temperature dependence of the resistivity due to the doping can explain the temperature dependence of T 1. The results are in agreement with the experimental data for La 2−xSr xCuO 2 system.

Theory of nuclear magnetic relaxation by anisotropic chemical shift II

Abstract Earlier calculations on nuclear magnetic relaxation by anisotropic chemical shift performed under the assumption that a certain term proportional to the asymmetry parameter is negligible have been revised so as to include the previously neglected term.

Molecular motion and nuclear magnetic relaxation in filled poly(vinyl acetate)

Molecular motion and nuclear magnetic relaxation were studied with samples of PVA filled with mica particles and fluoroplast-4, in the temperature range 25–150°C. By analysis of the shape of transversal and longitudinal magnetization decay curves it was found that segmental motion differs in the neighbourhood of the filler particles. It is assumed that the difference might be caused by interactions between the PVA macromolecules and fluoroplast-4. The non-exponential curves of the recovery of longitudinal and decay of transversal magnetization in samples filled with fluorplast and kica are described by the Bloembergen-Purcell-Pound theory of nuclear magnetic relaxation, with a log-normal distribution of the correlation times of segmental motion in macromolecules.

Nuclear magnetic relaxation in fractal pores.

The theory of nuclear magnetic relaxation of a fluid in a porous medium is applied to the case of a medium having a fractal structure resembling a Menger sponge. Rapid diffusion within a pore is assumed and the limiting cases of rapid and vanishing diffusion between pores are treated. The results are compared with experiments on two sandstone samples. There is good qualitative agreement with the case of vanishing interpore diffusion but poor quantitative agreement. It appears that the quantitative disagreement could be at least partially removed by including moderate diffusion between pores.

Theory of nuclear magnetic relaxation by dipolar interaction

A theoretical study is made of nuclear magnetic relaxation by dipole-dipole interactions, when the molecules containing the dipoles are subject to random thermal motion. Relaxation rates are expressed in terms of spectral densities for both intermolecular and intramolecular interactions. Analytical expressions for relaxation rates are derived in an inertial theory for various molecular models. Rotational diffusion results obtained for a spherical molecule may be applied to a linear or a symmetric molecule.

Theory of nuclear magnetic relaxation

A theory of nuclear magnetic relaxation centred around the rotation operator is proposed. The theory is applicable in principle to molecules of arbitrary shape, and account is taken of the effects of their inertia. Calculation of relaxation times associated with anisotropic chemical shift and spin-rotational interactions provides illustrations of how the theory may be employed.

Theory of nuclear magnetic relaxation by anisotropic chemical shift

A theory of nuclear magnetic relaxation by anisotropic chemical shift is based on an inertial theory of rotational Brownian motion of a molecule of arbitrary shape immersed in a liquid. Explicit expressions are derived for spherical, linear and symmetric rotator molecular models. These provide a generalization of results obtained by Abragam.

Nuclear magnetic relaxation in adsorbed helium-3 monolayers and other two-dimensional systems

The general theory of nuclear magnetic relaxation in homogeneous adsorbed systems is developed in a way which takes account of the specific features of two-dimensional motion. It is shown that the reduced dimensionality has the effect of decreasing the relaxation times from their naively expected values by as much as a few orders of magnitude, and of causing T1 and T2 to be unequal even in the presence of fast atomic motion. The theory is in close agreement with observed relaxation times of adsorbed helium-3.

Theory of nuclear magnetic relaxation in KCoF3 having residual orbital moment

In antiferromagnetic KCoF3 having residual orbital moment, a new mechanism of the nuclear spin-lattice relaxation involving strong magnon-phonon interaction is presented. The calculated temperature and field dependences of the relaxation time of the fluorine nuclear spin are in good agreement with the observed results.

Laser-pulse requirements for coherent and mode-selective excitation in the quasicontinuum of polyatomic molecules

We show that the theory of nuclear magnetic relaxation applies with equal validity to intramolecular relaxation in the quasicontinuum of polyatomic molecules. This theory permits an analysis of the laser-pulse requirements for vibrational-mode selectivity and coherent multiphoton excitation. The laser Rabi precession frequency, microepsilon/h, should exceed 1/T(1) or 1/T(2), the intramolecular relaxation rates in the quasicontinuum. In practice this requires either an ultra-fast optical-pulse risetime or a slower pulse that is tuned far to the red side of the transition.

Kinetic theory of NMR in dilute molecular gases. Existence of a minimum in the transverse relaxation time

A kinetic theory of nuclear magnetic relaxation in dilute molecular gases is proposed. The theory is based on the linearized Waldmann–Snider equation and developed from the standpoint of studying the fluctuation spectrum with the well-established methods of linear response theory. The main result of this work is the prediction of a minimum for the transverse relaxation time T2, in contrast to previously proposed theories.

Spin ? lattice relaxation in chlorofluorocarbon liquids

We have used the spin — echo method to measure spin — lattice relaxation times in liquid chlorofluorocarbons over a wide range of temperatures, frequencies, and molecular weights. Analysis of the experimental data shows that to determine the kinetic parameters of viscous liquids it is necessary to use the theory of nuclear magnetic relaxation by translational diffusion. We describe a method for the computer calculation of these parameters and discuss the results.

On the theory of nuclear magnetic relaxation by intermolecular dipole-dipole interaction

The expression for the nuclear magnetic relaxation rate due to intermolecular dipole-dipole interaction, previously derived for monoatomic liquids only, is worked out for molecular liquids. It contains the molecular pair distribution function which includes angular correlations.

Gas Phase Spin Relaxation of ZX3Y Molecules in the Dipolar Approximation

The gas kinetic theory of nuclear magnetic relaxation of a polyatomic gas, as formulated in the previous paper, is evaluated for ZX3Y molecules relaxing via a dipolar coupling Hamiltonian. Stress is given to a proper treatment of point group symmetry, here C3v, and the possibility of molecular inversion is included. The detailed formula for the spin traces is however restricted to X nuclei with spin 1/2. A subsequent paper uses these results to elucidate the structure of the high density dependence of T1 forCF3H.

Statistical theory of nuclear magnetic relaxation in the rotating frame

AbstractThe statistical theory of the nuclear magnetic relaxation of the spins in a rotating frame has been developed by the theoretical functional method of projecting operators (PO). This method of PO was used for finding the kinetic equation for the spin TCF. A general expression for the relaxation rates in the case of slow and fast thermal motion in the spirit of the well known Kubo‐Tomita theory is determined from the structure of these kinetic equations.

Relaxation studies VII. Nuclear magnetic relaxation due to gas-like rotation in liquids

A theory of nuclear magnetic relaxation in solution is developed for situations in which the molecules of interest can tumble in a way that resembles their rotation in the gas phase. The equations are constructed heuristically from the exact correlation function for the free axially symmetric top and the classical limit of the quantum-mechanical equation is obtained. In the limit when the symmetric top becomes a spherical top the equations are identical to these obtained on a classical model by Steele.

Nuclear magnetic relaxation in liquid ammonia and conditional inertial rotation in liquids

A theory of nuclear magnetic relaxation induced by inertial rotation in polar liquids is described. It is proposed that such rotation occurs only when the neighbourhood of a molecule attains an expanded lattice configuration. The non-markovian processes involved in the relaxation are expressed in terms of rate constants that occur in a formulation due to Anderson, and these are interpreted in terms of the unconditioned inertial rotation theory described in the preceding paper. The theory is used to interpret the values of T 1 obtained for 14N and D in liquid ammonia. The paper concludes with an outline of a general theory of anisotropic diffusion in liquids.