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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Picosecond Time-Resolved Resonance Raman Study of the Solvated Electron in Water
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Picosecond Time-Resolved Resonance Raman Study of the Solvated Electron in Water

机译：水中溶剂化电子的皮秒时间分辨共振拉曼研究

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摘要

Picosecond time-resolved Raman spectra of water were measured under the resonance condition with the electronic transition of the solvated electron. Transient Raman bands were observed in the OH bend and the OH stretch regions in accordance with the generation of the solvated electron. The lifetimes of the transient Raman bands were shortened by the addition of the electron scavenger, in exactly the same manner as the solvated electron absorption. It was concluded that the observed transient Raman bands are attributed to the water molecules that directly interact with the electron in the first solvation shell. The resonance enhancement factors were estimated as high as ～10~5 (the OH bend) and ～10~3 (the OH stretch) when the probe wavelength was tuned to the absorption maximum of the s → p transition of the solvated electron. The observed very high resonance enhancement indicated that the vibrational state of the solvating water molecules is strongly coupled with the electronic state of the electron. This implied that we should consider the electron and the solvating water molecules together (as a "quasi-molecule") when we discuss the vibronic state of the local solvgation structure. The probe wavelength dependence of the transient Raman intensity was examined in a wide range from 410 to 800 nm. The obtained excitation profiles suggested that the s → conduction transition does not significantly contribute to the resonance Raman enhancement. The polarized Raman measurement was also undertaken for the OH bend band. A nonzero depolarization ratio was observed, which showed that the nondegeneracy of the three sublevels in the excited p state can be observed on the time scale of the Raman process. The OH bending and OH stretching frequencies of the solvating water molecule are downshifted compared with the frequencies of the bulk water, indicating that a structural change is induced by the strong interaction with the electron.
机译：在共振条件下，随着溶剂化电子的电子跃迁，测量了水的皮秒时间分辨拉曼光谱。根据溶剂化电子的产生，在OH弯曲和OH拉伸区域中观察到瞬态拉曼带。通过添加电子清除剂，以与溶剂化电子吸收完全相同的方式缩短了瞬态拉曼能带的寿命。结论是，观察到的瞬态拉曼能带归因于与第一溶剂化壳中的电子直接相互作用的水分子。当探针波长调整到溶剂化电子的s→p跃迁的吸收最大值时，共振增强因子估计高达〜10〜5（OH弯曲）和〜10〜3（OH拉伸）。观察到的非常高的共振增强表明，溶剂化水分子的振动状态与电子的电子状态密切相关。这意味着当我们讨论局部溶剂化结构的振动状态时，我们应该将电子和溶剂化水分子一起考虑（作为“准分子”）。在410至800 nm的宽范围内检查了瞬态拉曼强度的探针波长依赖性。所获得的激发曲线表明，s→传导跃迁对共振拉曼增强没有显着贡献。还对OH弯曲带进行了极化拉曼测量。观察到非零的去极化率，这表明可以在拉曼过程的时间尺度上观察到处于激发p状态的三个亚能级的非简并性。与大量水的频率相比，溶剂化水分子的OH弯曲和OH拉伸频率下移，表明与电子的强相互作用引起结构变化。

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