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首页> 外文期刊>Journal of Non-Crystalline Solids: A Journal Devoted to Oxide, Halide, Chalcogenide and Metallic Glasses, Amorphous Semiconductors, Non-Crystalline Films, Glass-Ceramics and Glassy Composites >Fast stochastic librations and slow small-angle rotations of molecules in glasses observed on nitroxide spin probes by stimulated electron spin echo spectroscopy
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Fast stochastic librations and slow small-angle rotations of molecules in glasses observed on nitroxide spin probes by stimulated electron spin echo spectroscopy

机译：激发电子自旋回波谱仪在氮氧化物自旋探针上观察到的玻璃中分子的快速随机释放和缓慢的小角度旋转

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摘要

Electron spin echo (ESE) spectroscopy as applied to nitroxide spin probes in glasses is sensitive to molecular motions of two types. The first type of motion is fast stochastic librations, with correlation times on the scale of nanoseconds. In this work, these librations were found in glassy glycerol above similar to 190 K and in glassy o-terphenyl above similar to 250 K (glass transition temperatures for these two solvents are T-g = 185 K and T-g = 243 K, respectively). Most likely, these librations are of the same origin as anharmonic atomic vibrations, as seen in glasses by neutron scattering above a so-called dynamical transition temperature. The second type of motion is slow millisecond inertial rotations, which are observed in the experimentally accessible microsecond time scale as developing within an angular range of similar to 0.1-2 degrees. Over the temperature range studied, the square of the characteristic rotation rate was found to be proportional to the dielectric alpha-relaxation rate that is known for glycerol and o-terphenyl from literature. This empirical fact probably means that small-angle inertial rotations of spin probes and dielectric alpha-relaxation in the solvent are interrelated phenomena.
机译：电子自旋回波（ESE）光谱应用于玻璃中的一氧化氮自旋探针对两种类型的分子运动均敏感。第一种运动是快速随机释放，相关时间为纳秒级。在这项工作中，在高于190 K的玻璃状甘油和高于250 K的玻璃状邻三苯中发现了这些游离（这两种溶剂的玻璃化转变温度分别为T-g = 185 K和T-g = 243 K）。这些释放最有可能与非谐原子振动起源相同，正如在玻璃中通过所谓的动态转变温度以上的中子散射所看到的那样。第二种运动是缓慢的毫秒惯性旋转，这是在实验上可访问的微秒时间范围内观察到的，它是在类似于0.1-2度的角度范围内发展的。在研究的温度范围内，发现特征转速的平方与文献中已知的甘油和邻三联苯的介电α弛豫速率成正比。这个经验事实可能意味着自旋探针的小角度惯性旋转和溶剂中介电的α弛豫是相互关联的现象。

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