scispace - formally typeset
Search or ask a question
Topic

Relaxation (NMR)

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


Papers
More filters
Journal ArticleDOI
TL;DR: The physical content of three-point functions that relate the sensitivity of the averaged two-time dynamics to external control parameters (such as temperature or density) as well as their connection to the more standard four-point dynamic susceptibility associated with dynamical heterogeneities are discussed.
Abstract: We use recently introduced three-point dynamic susceptibilities to obtain an experimental determination of the temperature evolution of the number of molecules N corr that are dynamically correlated during the structural relaxation of supercooled liquids. We first discuss in detail the physical content of three-point functions that relate the sensitivity of the averaged two-time dynamics to external control parameters such as temperature or density, as well as their connection to the more standard four-point dynamic susceptibility associated with dynamical heterogeneities. We then demonstrate that these functions can be experimentally determined with good precision. We gather available data to obtain the temperature dependence of N corr for a large number of supercooled liquids over a wide range of relaxation time scales from the glass transition up to the onset of slow dynamics. We find that N corr systematically grows when approaching the glass transition. It does so in a modest manner close to the glass transition, which is consistent with an activation-based picture of the dynamics in glassforming materials. For higher temperatures, there appears to be a regime where N corr behaves as a power-law of the relaxation time. Finally, we find that the dynamic response to density, while being smaller than the dynamic response to temperature, behaves similarly, in agreement with theoretical expectations.

217 citations

Journal ArticleDOI
TL;DR: The van der Waals liquid ortho-terphenyl has been used as a model system in the study of the glass transition and extensive experiments have been undertaken to monitor the onset of structural relaxation on microscopic time and length scales.
Abstract: The van der Waals liquid ortho-terphenyl has long been used as a model system in the study of the glass transition. Motivated by mode-coupling theory, extensive experiments have been undertaken to monitor the onset of structural relaxation on microscopic time- and lengthscales. Using in particular quasielastic neutron scattering, the decay of density and tagged-particle correlations has been measured as a function of temperature, pressure and wavenumber. A consistent picture is developed, in which the mode-coupling singularity appears as a change of transport mechanism in the moderately viscous liquid, at temperatures far above the conventional (caloric) glass transition.

216 citations

Journal ArticleDOI
TL;DR: The results show an approximately linear increase in relaxation rate R2* with field strength for all tissues, leading to a greater range of relaxation times across tissue types at 7 T that can be exploited in high-resolution T2*-weighted imaging.

216 citations

Journal ArticleDOI
TL;DR: In this article, a spin-relaxation filter was used to separate the 1H nuclear magnetic resonance (NMR) resonances based on their relaxation times and allow simplification of the complex NMR spectra.

216 citations

Journal ArticleDOI
22 Oct 2004-Science
TL;DR: By resolving the binding energy of the excess electron in real time with femtosecond resolution, this work captured the ultrafast dynamics of the electron in the presolvated (“wet”) and hydrated states and obtained, as a function of cluster size, the subsequent relaxation times.
Abstract: We directly observed the hydration dynamics of an excess electron in the finite-sized water clusters of (H_2O)^-_n with n = 15, 20, 25, 30, and 35. We initiated the solvent motion by exciting the hydrated electron in the cluster. By resolving the binding energy of the excess electron in real time with femtosecond resolution, we captured the ultrafast dynamics of the electron in the presolvated (“wet”) and hydrated states and obtained, as a function of cluster size, the subsequent relaxation times. The solvation time (300 femtoseconds) after the internal conversion [140 femtoseconds for (H_2O)^-_35] was similar to that of bulk water, indicating the dominant role of the local water structure in the dynamics of hydration. In contrast, the relaxation in other nuclear coordinates was on a much longer time scale (2 to 10 picoseconds) and depended critically on cluster size.

216 citations


Network Information
Related Topics (5)
Amorphous solid
117K papers, 2.2M citations
88% related
Excited state
102.2K papers, 2.2M citations
87% related
Electron
111.1K papers, 2.1M citations
86% related
Band gap
86.8K papers, 2.2M citations
86% related
Raman spectroscopy
122.6K papers, 2.8M citations
86% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202227
2021652
2020582
2019614
2018638
2017645