Primary and secondary relaxation process in plastically crystalline cyanocyclohexane studied by 2H nuclear magnetic resonance. II. Quantitative analysis.
Primary and secondary relaxation process in plastically crystalline cyanocyclohexane studied by 2H nuclear magnetic resonance. II. Quantitative analysis.
复制标题
通过 2H 核磁共振研究塑性结晶氰基环己烷的初级和次级弛豫过程。
DOI：
10.1063/1.4790398
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
E. Rössler
中科院分区：
文献类型：
--
作者：
B. Micko;D. Kruk;E. Rössler
我们分析了我们先前报道的氰基环己烷塑性结晶（PC）相的2 H核磁共振（NMR）实验结果（本工作的第一部分），以详细研究快速次级弛豫（或β-过程）。自旋-晶格弛豫T1中额外最小值的出现和在玻璃化转变温度T（g）= 134 K以上的固体回波谱中出现的显著效应两者允许根据“锥内摆动”模型直接确定β过程的限制几何形状。而在低于T（g）的温度下，重取向被限制在相当小的立体角（低于10°），空间限制随着温度高于T（g）而强烈减小，即，锥角的分布连续地向更高的值移动。氰基环己烷PC相中的β-过程通过与结构玻璃形成剂中发现的相同机制进行。这通过证明自旋晶格弛豫、受激回波衰减和谱参数的非常相似的行为（对于T < T（g））来证实，当绘制为（取自介电谱）的函数时。然而，我们没有观察到NMR观察到的β过程的弛豫强度（在锥内摆动模型中计算）与介电谱之间的明确关系。
We analyze the results of our previously reported 2H nuclear magnetic resonance (NMR) experiments in the plastically crystalline (PC) phase of cyanocyclohexane (Part I of this work) to study the fast secondary relaxation (or β-process) in detail. Both, the occurrence of an additional minimum in the spin-lattice relaxation T1 and the pronounced effects arising in the solid-echo spectrum above the glass transition temperature T(g) = 134 K, allow for a direct determination of the restricting geometry of the β-process in terms of the "wobbling-in-a-cone" model. Whereas at temperatures below T(g) the reorientation is confined to rather small solid angles (below 10°), the spatial restriction decreases strongly with temperature above T(g), i.e., the distribution of cone angles shifts continuously towards higher values. The β-process in the PC phase of cyanocyclohexane proceeds via the same mechanism as found in structural glass formers. This is substantiated by demonstrating the very similar behavior (for T < T(g)) of spin-lattice relaxation, stimulated echo decays, and spectral parameters when plotted as a function of (taken from dielectric spectroscopy). We do, however, not observe a clear-cut relation between the relaxation strength of the β-process observed by NMR (calculated within the wobbling-in-a-cone model) and dielectric spectroscopy.
影响因子：
4.4
作者：
Gainaru, C.;Lips, O.;Roessler, E. A.
通讯作者：
Roessler, E. A.
分子玻璃形成体动态磁化率的演变：光散射、介电谱和核磁共振的结果
DOI：
10.1063/1.4770055
发表时间：
2013
期刊：
The Journal of chemical physics
影响因子：
--
作者：
N. Petzold;B. Schmidtke;R. Kahlau;D. Bock;R. Meier;B. Micko;D. Kruk;E.A. Rössler
通讯作者：
E.A. Rössler