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Relaxation (NMR)

About: Relaxation (NMR) is a research topic. Over the lifetime, 29342 publications have been published within this topic receiving 689851 citations.


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Journal ArticleDOI
TL;DR: In this article, the most important spin relaxation mechanisms are considered and the spin relaxation times are calculated taking into account the contributions to the spin-orbit interaction due to the bulk inversion asymmetry and to the structure inverse asymmetry.
Abstract: Spin relaxation is investigated theoretically in two-dimensional systems. Various semiconductor structures of both n and p types are studied in detail. The most important spin relaxation mechanisms are considered. The spin relaxation times are calculated taking into account the contributions to the spin-orbit interaction due to the bulk inversion asymmetry and to the structure inversion asymmetry. It is shown that in-plane anisotropy of electron spin relaxation appears in III-V asymmetrical heterostructures. This anisotropy may be controlled by external parameters, and the spin relaxation times differ by several orders of magnitude.

148 citations

Journal ArticleDOI
TL;DR: In this article, the authors describe the generalization of the Bloch equation in terms of Caputo fractional derivatives of order α (0 < α < 1) for a single spin system in a static magnetic field at resonance.
Abstract: Nuclear magnetic resonance (NMR) is a physical phenomenon widely used in chemistry, medicine, and engineering to study complex materials. NMR is governed by the Bloch equation, which relates a macroscopic model of magnetization to applied radiofrequency, gradient and static magnetic fields. Simple models of materials are well described by the classical first order dynamics of precession and relaxation inherent in the vector form of the Bloch equation. Fractional order generalization of the Bloch equation presents an opportunity to extend its use to describe a wider range of experimental situations involving heterogeneous, porous, or composite materials. Here we describe the generalization of the Bloch equation in terms of Caputo fractional derivatives of order α (0 < α < 1) for a single spin system in a static magnetic field at resonance. The results are expressed in terms of the Mittag–Leffler function—a generalized exponential function that converges to the classical case when α = 1. © 2009 Wiley Periodicals, Inc. Concepts Magn Reson Part A 34A: 16–23, 2009.

148 citations

Journal ArticleDOI
TL;DR: The nuclear-spin relaxation rate of gaseous [sup 3]He due to the magnetic-dipole interaction between the nuclear spins is derived, and this dipolar relaxation rate is numerically evaluated for temperatures from 0.1 K to 550 K.
Abstract: We derive the nuclear-spin relaxation rate of gaseous $^{3}\mathrm{He}$ due to the magnetic-dipole interaction between the $^{3}\mathrm{He}$ nuclear spins. This dipolar relaxation rate is numerically evaluated for temperatures from 0.1 K to 550 K. At room temperature, the relaxation time for a $^{3}\mathrm{He}$ density of 10 amagats is 74.4 h. We have made a series of high-density (4--12 amagat) $^{3}\mathrm{He}$ samples for which nulcear relaxation is limited by the magnetic-dipole interaction. Both our theoretical and experimental results are particularly important for the growing use of $^{3}\mathrm{He}$, polarized through spin exchange with optically pumped Rb vapor.

148 citations

Journal ArticleDOI
TL;DR: In this article, the electron transfer is controlled by protein motion in photosynthetic reaction centers using molecular dynamics simulations of two electron transfer steps in the reaction center of Rps viridis at physiological and at lower temperatures.

148 citations

Journal ArticleDOI
TL;DR: The periodic shell structure and surface reconstruction of metallic FePt nanoparticles with icosahedral structure has been quantitatively studied by high-resolution transmission electron microscopy with focal series reconstruction with sub-angstrom resolution and finds the lattice spacing of (111) planes in the surface region to be size dependent.
Abstract: The periodic shell structure and surface reconstruction of metallic FePt nanoparticles with icosahedral structure has been quantitatively studied by high-resolution transmission electron microscopy with focal series reconstruction with sub-angstrom resolution. The icosahedral FePt nanoparticles fabricated by the gas phase condensation technique in vacuum have been found to be surprisingly oxidation resistant and stable under electron beam irradiation. We find the lattice spacing of (111) planes in the surface region to be size dependent and to expand by as much as 9% with respect to the bulk value of Fe52Pt48. Controlled removal of the (111) surface layers in situ results in a similar outward relaxation of the new surface layer. This unusually large layerwise outward relaxation is discussed in terms of preferential Pt segregation to the surface forming a Pt enriched shell around a Fe-rich Fe/Pt core.

148 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202227
2021652
2020582
2019614
2018638
2017645