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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.


Papers
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Journal ArticleDOI
S. Lüsse1, K. Arnold1
TL;DR: In this article, a model of fast exchange of water molecules between a bound and an unbound water fraction was proposed to estimate the number of bound water molecules per PEG repeat unit.
Abstract: In this paper NMR relaxation time investigations of water protons (1H) and deuterons (2H) in aqueous poly(ethylene glycol) (PEG) solutions are presented for the water content range of 3−90 wt %. The number of bound water molecules per PEG repeat unit is estimated to be one from the water relaxation times by using a model of fast exchange of water molecules between a bound and an unbound water fraction. For water contents lower than one water molecule per PEG monomer, large restrictions in polymer mobility occur which also influence water NMR relaxation. For these low water contents, small ranges of oriented PEG chains are present in the solutions resulting in observable quadrupole splittings in the 2H NMR spectra.

174 citations

Journal ArticleDOI
TL;DR: It is shown that a relaxation process which exhibits a Gaussian distribution in the logarithm of the relaxation times (a "lognormal" distribution) can be specified completely by three parameters: the mean relaxation time (τm), width of the distribution (β), and the magnitude of the Relaxation (δJ).
Abstract: Such phenomena as dielectric, magnetic, and anelastic relaxation are often described in terms of a distribution of relaxation times. It is shown that a relaxation process which exhibits a Gaussian distribution in the logarithm of the relaxation times (a "lognormal" distribution) can be specified completely by three parameters. These are: the mean relaxation time (τm) the, width of the distribution (β), and the magnitude of the relaxation (δJ). The relationships of these parameters to experimentally measurable functions are usually complicated. These relationships were obtained in numerical form by machine computation. Finally, a simple formula is derived which expresses the parameter β in terms of the widths of the distribution of the activation energies and that of the attempt frequencies.

174 citations

Journal ArticleDOI
TL;DR: Kinetic Monte Carlo simulations of fcc clusters show that the usual theories of equilibration, via atomic surface diffusion driven by curvature, are verified only at high temperatures, with an exponential dependence of the relaxation time.
Abstract: What are the mechanisms leading to the shape relaxation of three-dimensional crystallites? Kinetic Monte Carlo simulations of fcc clusters show that the usual theories of equilibration, via atomic surface diffusion driven by curvature, are verified only at high temperatures. Below the roughening temperature, the relaxation is much slower, kinetics being governed by the nucleation of a critical germ on a facet. We show that the energy barrier for this step linearly increases with the size of the crystallite, leading to an exponential dependence of the relaxation time.

174 citations

Journal ArticleDOI
TL;DR: Compounds 2 and 3 exhibit slow relaxation of the magnetization up to 4 K under an applied dc field, indicating SMM behavior.

174 citations

Book
13 Jul 1995
TL;DR: In this article, the authors introduce chemical shifts and chemical exchange for spin spin coupling and spin relaxation, as well as spin-spin coupling with chemical exchange and spinner spin relaxation.
Abstract: 1. Introduction 2. Chemical shifts 3. Spin-spin coupling 4. Chemical exchange 5. Spin relaxation 6. Experimental methods Bibliography Index

174 citations


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