INTERMOLECULAR MULTIPLE-QUANTUM COHERENCES AND CROSS CORRELATIONS IN SOLUTION NUCLEAR-MAGNETIC-RESONANCE
INTERMOLECULAR MULTIPLE-QUANTUM COHERENCES AND CROSS CORRELATIONS IN SOLUTION NUCLEAR-MAGNETIC-RESONANCE
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DOI：
10.1063/1.464770
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发表时间：
1993-05-01
影响因子：
4.4
通讯作者：
WARREN, WS
中科院分区：
文献类型：
--
作者：
HE, QH;RICHTER, W;WARREN, WS
最近有报道称，在水和其他浓缩样品中明显可以观察到多量子核磁共振相干性，这直接违反了既定理论。这些结果在之前的衣态框架中被解释为自旋和线圈之间耦合的表现（量子化辐射阻尼）。在这里，我们提供了先前传播的这些效应的实验探索的细节[J]。化学。物理学，96,1659(1992)]，我们将这些结果扩展到多成分样本。我们在二维实验中观察到溶液中独立分子之间的交叉峰，包括具有多量子相干转移回波的光谱；我们还证明了溶剂和（稀）溶质分子之间的相干转移。然而，我们表明这些分子间交叉峰是由局部机制引起的，因此辐射阻尼（经典或量子化）不能提供它们发生的大部分解释。模拟和分析结果表明，偶极退磁场可以解释许多这些令人惊讶的影响，尽管一个完整的画面必须更加复杂。
It was recently reported that multiple-quantum NMR coherences could apparently be observed in water and other concentrated samples, in direct violation of established theory. These results were previously explained in a dressed-state framework as manifestations of the coupling between the spins and the coil (quantized radiation damping). Here we provide details of previously communicated experimental explorations of these effects [J. Chem. Phys. 96, 1659 (1992)], and we extend these results to multicomponent samples. We observe cross peaks between independent molecules in solution in two-dimensional experiments, including spectra with multiple-quantum coherence transfer echoes; we also demonstrate coherence transfer between solvent and (dilute) solute molecules. However, we show that these intermolecular cross peaks are induced by a mechanism which is local in nature, and thus radiation damping (either classical or quantized) cannot provide the bulk of the explanation for their occurrence. Simulations and analytical results show that the dipolar demagnetizing field can account for many of these surprising effects, although a complete picture must be more complex.