Theory of long-lived nuclear spin states in solution nuclear magnetic resonance. I. Singlet states in low magnetic field
Theory of long-lived nuclear spin states in solution nuclear magnetic resonance. I. Singlet states in low magnetic field
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DOI：
10.1063/1.1893983
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发表时间：
2005-06-01
影响因子：
4.4
通讯作者：
Levitt, MH
中科院分区：
文献类型：
--
作者：
Carravetta, M;Levitt, MH
我们最近证明了在溶液态核磁共振中存在超长寿命的核自旋态。在含有耦合自旋对-1/2的系统中，核自旋单重态的寿命可能比传统的弛豫时间常数T-1高一个数量级以上。如果阻止长寿命的单线态与快速弛豫的三重态混合，则可以观察到这些长寿命。本文给出了一个利用磁场循环观测慢单重态弛豫的实验的详细理论。利用分子内偶极-偶极耦合模型和起伏的外部随机场，给出了单重态弛豫速率常数随磁场变化的近似表达式。(C)2005年美国物理研究所。
We have recently demonstrated the existence of exceptionally long-lived nuclear spin states in solution-state nuclear magnetic resonance. The lifetime of nuclear spin singlet states in systems containing coupled pairs of spins-1/2 may exceed the conventional relaxation time constant T-1 by more than an order of magnitude. These long lifetimes may be observed if the long-lived singlet states are prevented from mixing with rapidly relaxing triplet states. In this paper we provide the detailed theory of an experiment which uses magnetic field cycling to observe slow singlet relaxation. An approximate expression is given for the magnetic field dependence of the singlet relaxation rate constant, using a model of intramolecular dipole-dipole couplings and fluctuating external random fields. (c) 2005 American Institute of Physics.