期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 135, 期 50, 页码 18746-18749出版社
AMER CHEMICAL SOC
DOI: 10.1021/ja410432f
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资金
- Engineering and Physical Sciences Research Council (UK)
- European Research Council
- Wolfson Foundation
- Engineering and Physical Sciences Research Council [EP/D079209/1, EP/I036141/1, EP/K00509X/1] Funding Source: researchfish
- EPSRC [EP/D079209/1, EP/K00509X/1, EP/I036141/1] Funding Source: UKRI
Substances containing rapidly rotating methyl groups may exhibit long-lived states (LLSs) in solution, with relaxation times substantially longer than the conventional spin-lattice relaxation time T-1. The states become long-lived through rapid internal rotation of the CH3 group, which imposes an approximate symmetry on the fluctuating nuclear spin interactions. In the case of very low CH3 rotational barriers, a hyperpolarized LLS is populated by thermal equilibration at liquid helium temperature. Following dissolution, cross-relaxation of the hyperpolarized LLS, induced by heteronuclear dipolar couplings, generates strongly enhanced antiphase NMR signals. This mechanism explains the NMR signal enhancements observed for C-13-gamma-picoline (Icker, M.; Berger, S. J. Magn. Reson. 2012, 219, 1-3).
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