Water dynamics on ice and hydrate lattices studied by second-order central-line stimulated-echo oxygen-17 nuclear magnetic resonance.
Water dynamics on ice and hydrate lattices studied by second-order central-line stimulated-echo oxygen-17 nuclear magnetic resonance.
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DOI：
10.1063/1.4936416
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发表时间：
2015-12
期刊：
影响因子：
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通讯作者：
M. Adjei-Acheamfour;J. F. Tilly;Joachim Beerwerth;R. Böhmer
中科院分区：
文献类型：
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作者：
M. Adjei-Acheamfour;J. F. Tilly;Joachim Beerwerth;R. Böhmer
Oxygen-17 受激回波光谱是一种新型核磁共振 (NMR) 技术，可用于研究含氧材料中超慢分子运动的时间尺度和几何结构。该方法基于检测氧中心跃迁核磁共振线内由二阶四极相互作用引起的定向编码频率变化。除了后者之外，目前对各种双脉冲回波和受激回波脉冲序列的理论分析还考虑了异核偶极相互作用。作为实验实例，通过两次氧17受激回波相关函数研究了四氢呋喃笼形水合物多晶中的超慢水运动。由此产生的相关时间和六方冰的相关时间与之前的氘核核磁共振测量结果相似。将各种运动模型的回波函数最终状态相关性的计算与笼形水合物的实验数据进行比较。结果发现，包括氧-质子偶极相互作用的六位点模型描述了当前的结果。
Oxygen-17 stimulated-echo spectroscopy is a novel nuclear magnetic resonance (NMR) technique that allows one to investigate the time scale and geometry of ultraslow molecular motions in materials containing oxygen. The method is based on detecting orientationally encoded frequency changes within oxygen's central-transition NMR line that are caused by second-order quadrupolar interactions. In addition to the latter, the present theoretical analysis of various two-pulse echo and stimulated-echo pulse sequences takes also heteronuclear dipolar interactions into account. As an experimental example, the ultraslow water motion in polycrystals of tetrahydrofuran clathrate hydrate is studied via two-time oxygen-17 stimulated-echo correlation functions. The resulting correlation times and those of hexagonal ice are similar to those from previous deuteron NMR measurements. Calculations of the echo functions' final-state correlations for various motional models are compared with the experimental data of the clathrate hydrate. It is found that a six-site model including the oxygen-proton dipolar interaction describes the present results.