...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Applied Magnetic Resonance >CW EPR, echo-detected EPR, and field-step ELDOR study of molecular motions of nitroxides in o-terphenyl glass: Dynamical transition, dynamical heterogeneity and beta-relaxation
【24h】

CW EPR, echo-detected EPR, and field-step ELDOR study of molecular motions of nitroxides in o-terphenyl glass: Dynamical transition, dynamical heterogeneity and beta-relaxation

机译：连续EPR，回波检测EPR和场步ELDOR研究邻三联苯玻璃中氮氧化物的分子运动：动态跃迁，动态异质性和β松弛

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Continuous-wave electron paramagnetic resonance (CW EPR), echo-detected (ED) EPR, and field-step electron-electron double resonance (FS ELDOR) were simultaneously applied to study molecular motions of nitroxide spin probes of two different types in glassy o-terphenyl. A strong linear temperature dependence of the overall splitting of the CW EPR lineshape was found for nitroxide Tempone and only a weak one for a phenyl-ring-containing imidasoline nitroxide. The linear temperature dependence of the splitting is explained within the model of harmonic librations. The assessed libration frequency for Tempone is of the order of 3.10(12) rad/s. The observed remarkable difference between the two nitroxides is explained by the different strength of interactions between guest and host molecules and by dynamical heterogeneity of the glass. The nonlinear temperature dependence above 250 K is attributed to the onset of anharmonic motion that is postulated in a number of neutron scattering and Mossbauer spectroscopy studies for molecular glasses and proteins (the so-called dynamical transition). Above 245 K also ED EPR spectra change drastically, which may be explained on the same ground. Magnetization transfer was observed in FS ELDOR for nitroxide Tempone, with a time constant around 10(-5) s. It was found to be almost temperature-independent between 160 K and 265 K and was attributed to the Johari-Goldstein beta-relaxation process. For the phenyl-ring-containing imidasoline nitroxide this transfer was not observed, which may be explained again by the dynamical heterogeneity of the glass and by small effectivity of the relaxation process in this case.
机译：同时应用连续波电子顺磁共振（CW EPR），回波检测（ED）EPR和场步电子-电子双共振（FS ELDOR）来研究两种不同类型的硝化自旋探针在玻璃质中的分子运动-三苯基。对于氮氧化物Tempone，发现CW EPR线形的整体分裂具有很强的线性温度依赖性，而对于含苯环的咪唑啉氮氧化物，只有很弱的线性温度依赖性。在谐波释放模型中解释了分裂的线性温度依赖性。 Tempone的估计释放频率约为3.10（12）rad / s。客体和主体分子之间相互作用的强度不同以及玻璃的动态异质性解释了两种氮氧化物之间观察到的显着差异。高于250 K的非线性温度依赖性归因于非谐运动的开始，这在分子玻璃和蛋白质的中子散射和Mossbauer光谱学研究中被假定（所谓的动态跃迁）。高于245 K时，ED EPR光谱也会急剧变化，这可以在同一背景下解释。在FS ELDOR中观察到氮氧化物Tempone的磁化转移，时间常数约为10（-5）s。发现它在160 K和265 K之间几乎与温度无关，并且归因于Johari-Goldsteinβ松弛过程。对于含苯环的咪唑啉氮氧化物，未观察到这种转移，这可以再次由玻璃的动态异质性和这种情况下松弛过程的小的作用来解释。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号