Distortion Correction of Low-Energy Photoelectron Spectra of Liquids Using Spectroscopic Data for Solvated Electrons
Distortion Correction of Low-Energy Photoelectron Spectra of Liquids Using Spectroscopic Data for Solvated Electrons
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DOI：
10.1021/acs.jpca.2c08046
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发表时间：
2023-03-14
影响因子：
2.9
通讯作者：
Suzuki，Toshinori
中科院分区：
文献类型：
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作者：
Yamamoto，Yo-ichi;Suzuki，Toshinori
时间分辨光电子能谱（TRPES）可以实时观察溶液中的超快电子动力学。当采用极紫外（EUV）探测脉冲时，它们可以将溶质从动力学中涉及的所有电子态中分离出来。然而，EUV脉冲还从溶剂产生强电离信号，其通常比溶质的泵浦-探测光电子信号大6个数量级。或者，UV探针脉冲能够对光激发的溶质进行高灵敏度和选择性的观察，因为典型的溶剂如水对UV辐射是透明的。这种UV-TRPES测量中的障碍是由电子散射引起的光谱失真和液体中尚未确定的机制。我们以前提出的光谱检索（SR）方法作为anaposterioriapproach消除失真，克服这个困难，在UV-TRPES，但是，它的准确性尚未得到验证，通过比较与EUV-TRPES结果。在本研究中，我们进行了UV-TRPES在水，甲醇和乙醇中的电荷转移反应，并验证SR分析的UV-TRPES。我们还估计了一个先前未确定的能量依赖的强度因子，并扩大了SR分析的基组。用改进的SR方法重新分析了UV-TRPES数据，研究了不同体系中溶剂化电子的形成和弛豫动力学。在液态水、甲醇和乙醇中溶剂化电子的电子结合能分布被确认为分别以3.78、3.39和3.25 eV为中心的高斯分布，与Nishitani等人[Sci. Adv.2019，5（8），eaaw6896]。在气液界面的导带和真空能级之间的有效能隙估计为0.2 eV的液态水和0.1 eV的甲醇和乙醇。
Time-resolved photoelectron spectroscopy (TRPES) enables real-time observation of ultrafast electronic dynamics in solutions. When extreme ultraviolet (EUV) probe pulses are employed, they can ionize solutes from all electronic states involved in the dynamics. However, EUV pulses also produce a strong ionization signal from a solvent that is typically 6 orders of magnitude greater than the pump–probe photoelectron signal of solutes. Alternatively, UV probe pulses enable highly sensitive and selective observation of photoexcited solutes because typical solvents such as water are transparent to UV radiation. An obstacle in such UV-TRPES measurements is spectral distortion caused by electron scattering and a yet to be identified mechanism in liquids. We have previously proposed the spectral retrieval (SR) method as ana posterioriapproach to removing the distortion and overcoming this difficulty in UV-TRPES; however, its accuracy has not yet been verified by comparison with EUV-TRPES results. In the present study, we perform EUV-TRPES for charge transfer reactions in water, methanol, and ethanol, and verify SR analysis of UV-TRPES. We also estimate a previously undetermined energy-dependent intensity factor and expand the basis sets for SR analysis. The refined SR method is employed for reanalyzing the UV-TRPES data for the formation and relaxation dynamics of solvated electrons in various systems. The electron binding energy distributions for solvated electrons in liquid water, methanol, and ethanol are confirmed to be Gaussian centered at 3.78, 3.39, and 3.25 eV, respectively, in agreement with Nishitani et al. [Sci. Adv.2019, 5(8), eaaw6896]. An effective energy gap between the conduction band and the vacuum level at the gas–liquid interface is estimated to be 0.2 eV for liquid water and 0.1 eV for methanol and ethanol.