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Titolo:
Variable temperature study of the cross-relaxation dynamics in the hyperpolarized xenon-induced enhancement of surface nuclei
Autore:
Smith, LJ; Smith, J; MacNamara, E; Knagge, K; Raftery, D;
Indirizzi:
Purdue Univ, Dept Chem, HC Brown Lab, W Lafayette, IN 47907 USA Purdue Univ W Lafayette IN USA 47907 Brown Lab, W Lafayette, IN 47907 USA
Titolo Testata:
JOURNAL OF PHYSICAL CHEMISTRY B
fascicolo: 7, volume: 105, anno: 2001,
pagine: 1412 - 1421
SICI:
1520-6106(20010222)105:7<1412:VTSOTC>2.0.ZU;2-2
Fonte:
ISI
Lingua:
ENG
Soggetto:
LASER-POLARIZED XENON; SOLID-STATE NMR; IN-SITU NMR; CONTINUOUS-FLOW; RECENT PROGRESS; XE-129 NMR; NOBLE-GAS; CATALYSTS; DIFFUSION; MRI;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
58
Recensione:
Indirizzi per estratti:
Indirizzo: Raftery, D Purdue Univ, Dept Chem, HC Brown Lab, W Lafayette, IN 47907 USAPurdue Univ W Lafayette IN USA 47907 W Lafayette, IN 47907 USA
Citazione:
L.J. Smith et al., "Variable temperature study of the cross-relaxation dynamics in the hyperpolarized xenon-induced enhancement of surface nuclei", J PHYS CH B, 105(7), 2001, pp. 1412-1421

Abstract

The cross-relaxation rate constants for a three spin system involving hyperpolarized Xe-129, C-13, and H-1 nuclei have been determined over a wide temperature range (136-216 K) through observation of the polarization enhancements from spin polarization induced nuclear Overhauser effect (SPINOE) experiments. A model system of methoxy groups adsorbed on high surface area silica was studied. A maximum polarization enhancement of 3.4 was observed for the methoxy carbon. Xenon-carbon and xenon-proton cross-relaxation were found to be dependent on both the xenon coverage and xenon diffusion across the silica surface. The temperature dependence of the cross-relaxation rateconstants was effectively fit using a hopping model. Possible improvementsfor the SPINOE experiment are suggested including alternative substrates which would retard xenon diffusion across the surface and improve xenon-carbon cross-relaxation leading to significantly larger SPINOE enhancements.

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Documento generato il 06/04/20 alle ore 08:09:43