Observation of molecular reorientation in ice by proton and deuterium magnetic resonance
Observation of molecular reorientation in ice by proton and deuterium magnetic resonance
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通过质子和氘磁共振观察冰中的分子重新取向
DOI：
10.1021/ja00225a013
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发表时间：
1988
影响因子：
15
通讯作者：
A. Pines
中科院分区：
文献类型：
--
作者：
R. Wittebort;M. Usha;D. Ruben;D. Wemmer;A. Pines
氘核磁共振和氘去偶质子核磁共振直接观察到了多晶六方冰（Ice I/sub h/）中的分子重取向。动力学被看作是粉末图案的交换加宽。根据各向异性自旋相互作用的大小，对图案产生类似效果所需的重取向速率按比例缩放，对于质子屏蔽各向异性，约为/ 6 kHz，或者对于水中的氘四极耦合，约为/ 200 kHz。由于这两种相互作用的大小不同，这两种方法对于研究200-267 K温度范围内的再取向是互补的。结果表明，水分子在冰中重新取向时具有四面体对称性。线形模拟使用四面体重取向的假设是在雅阁与实验光谱，并给出直接与温度相关的德拜相关时间，/tau//sub D/，从介电弛豫率。参考文献16篇，附图4幅。
Molecular reorientation in polycrystalline hexagonal ice, ice I/sub h/, has been directly observed by deuterium NMR and deuterium-decoupled proton NMR. The dynamics are seen as exchange broadening of powder patterns. The reorientational rates required to produce similar effects on the patterns are scaled according to the magnitudes of the anisotropic spin interactions, /approximately/ 6 kHz for the proton-shielding anisotropy or /approximately/ 200 kHz for the deuterium quadrupolar coupling in water. Because of the differing sizes of these two interactions, the two methods are complementary for studying reorientation over the temperature range 200-267 K. The results show that water molecules reorient with tetrahedral symmetry in ice. Line-shape simulations using the assumption of tetrahedral reorientation are in accord with the experimental spectra and give rates directly comparable to the temperature-dependent Debye correlation time, /tau//sub D/, from dielectric relaxation. 16 references, 4 figures.