...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Electron Spin-Lattice Relaxation Processes of Radicals in Irradiated Crystalline Organic Compounds
【24h】

Electron Spin-Lattice Relaxation Processes of Radicals in Irradiated Crystalline Organic Compounds

机译：辐照结晶有机化合物中自由基的电子自旋晶格弛豫过程

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

Electron spin-lattice relaxation times (T_(le)) for the major radicals in γ-irradiated polycrystalline samples of glycylglycine, L-alanine, 2,4,6-tri-butyl-phenol, and 4-methyl-2,6-di-tert-butyl-phenol were measured as a function of temperature using pulsed EPR. CW-saturation recovery (CW-SR) were obtained at X-band (9.1 GHz) and S-band (3.0 GHz) between about 10 and 295 K. Inversion recovery, echo-detected saturation recovery (ED-SR), and pulsed electron-electron double resonance (ELDOR) curves were obtained at X-band between 77 and about 295 K. For 2,4,6-tri-tert-butyl-phenoxy radical, which has a single-line EPR spectrum, the recovery times obtained by the three methods were in good agreement and were assigned as T_(le). For the three radicals with resolved hyperfine splitting, spectral diffusion caused the recovery times observed by inversion recovery or ED-SR to be significantly shorten than T_(le) obtained by CW-SR or ELDOR. Spectral diffusion processes were observed directly by pulsed ELDOR experiments, and time constants for cross relaxation and nuclear relaxation were obtained by modeling the ELDOR curves. For irradiated L-alanine and for the 4-methyl-2,6-tert-butyl-phenoxy radical at some temperatures, the effects of rapid cross relaxation on CW-SR curves could not be fully mitigated even by long saturating pulses, and T_(le) could only be determined by ELDOR. For the radicals in γ-irradiated L-alanine, 2,4,6-tri-tert-butyl-phenol, and 4-methyl-2,6-di-tert-butyl-phenol, methyl group rotation makes significant contributions to T_(le) at te,peratures where the rate of rotation of a methyl group is comparable to the microwave frequency. Activation energies for methyl rotation were determined by modeling the temperature dependence of T_(le) at X-band and S-band. In temperature ranges where methyl rotation did not dominate, T_(le) was dominated by Raman, direct, or local mode processes.
机译：γ-辐射的甘氨酰甘氨酸，L-丙氨酸，2,4,6-三丁基苯酚和4-甲基-2,6-多晶样品中主要自由基的电子自旋晶格弛豫时间（T_（le））使用脉冲EPR测量二叔丁基苯酚随温度的变化。在大约10到295 K之间的X波段（9.1 GHz）和S波段（3.0 GHz）上获得了CW饱和度恢复（CW-SR）。反向恢复，回波检测到的饱和度恢复（ED-SR）和脉冲在77到295 K之间的X波段获得了电子-电子双共振（ELDOR）曲线。对于具有单线EPR谱的2,4,6-三叔丁基-苯氧基自由基，其恢复时间通过三种方法获得的结果吻合良好，并指定为T_（le）。对于具有超细分裂拆分的三个自由基，光谱扩散导致通过反相恢复或ED-SR观察到的恢复时间比CW-SR或ELDOR获得的T_（le）显着缩短。通过脉冲ELDOR实验直接观察到光谱扩散过程，并通过对ELDOR曲线建模来获得交叉弛豫和核弛豫的时间常数。对于辐照的L-丙氨酸和在某些温度下的4-甲基-2,6-叔丁基-苯氧基自由基，即使通过较长的饱和脉冲也无法完全缓解快速交叉弛豫对CW-SR曲线的影响，并且T_ （le）只能由ELDOR确定。对于γ辐照的L-丙氨酸，2,4,6-三叔丁基苯酚和4-甲基-2,6-二叔丁基苯酚中的自由基，甲基旋转对T_的贡献很大。 （le）在te时，甲基的旋转速率与微波频率相当。通过模拟X波段和S波段T_（le）的温度依赖性，确定甲基旋转的活化能。在甲基旋转不占主导的温度范围内，T_（le）由拉曼，直接或局部模式过程主导。

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