Thürmer Stephan, Stemer Dominik, Trinter Florian, Kiyan Igor Yu, Winter Bernd, Wilkinson Iain
Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo, 606-8501 Kyoto, Japan.
Molecular Physics Department, Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany.
J Am Chem Soc. 2025 Jun 11;147(23):19868-19877. doi: 10.1021/jacs.5c04263. Epub 2025 Jun 2.
Experimental insights into low-kinetic-energy electron scattering in aqueous solutions are essential for an improved understanding of electron-driven chemistry and radiobiology, and the development and informed application of aqueous-phase electron-based spectroscopy and dichroism methods. Generally, in aqueous environments and for electron kinetic energies below 12-15 eV, significant and, thus far, incompletely understood low-energy-transfer inelastic electron scattering with solvent molecules preponderates. This leads to cascades of tens-of-meV kinetic-energy losses that distort nascent photoelectron spectra, prevent direct and accurate electron-binding-energy measurements, and limit possibilities to determine electron-scattering cross sections at especially low electron kinetic energies. Here, we quantify aqueous-phase inelastic-scattering-based energy losses using 1-30 eV kinetic energy photoelectrons and liquid-jet photoemission spectroscopy, specifically by photoionizing an exemplary surface-active solute and comparing the results with those from the homogeneously distributed aqueous solvent. Thereby, we identify a general ≳17 eV electron-kinetic-energy requirement for the direct and accurate measurement of aqueous-phase electron binding energies, irrespective of interfacial concentration profiles. Further, at electron kinetic energies from 10 eV down to a few-eV above the ionization threshold, we observe and quantify lower degrees of scattering for photoelectrons generated from surface-active solutes, allowing moderately distorted surface-active-solute photoemission peaks to be resolved down to just few-eV electron kinetic energies. These results demonstrate that liquid-jet photoemission spectroscopy can be used to probe interfacial surface-active-solute dynamics and dichroism effects close to ionization thresholds, in stark contrast to similar experiments on homogeneously distributed solution components. Furthermore, they offer novel insights into low-electron-kinetic-energy scattering in aqueous environments, thereby addressing the current lack of reliable experimental data in this critical energy range.
对水溶液中低动能电子散射的实验性见解对于更好地理解电子驱动化学和放射生物学，以及基于水相电子的光谱学和二向色性方法的开发与明智应用至关重要。一般来说，在水性环境中且电子动能低于12 - 15电子伏特时，与溶剂分子发生的显著且迄今尚未完全理解的低能量转移非弹性电子散射占主导。这会导致数十毫电子伏特的动能损失级联，从而扭曲初生光电子能谱，妨碍直接和准确的电子结合能测量，并限制在特别低的电子动能下确定电子散射截面的可能性。在此，我们使用1 - 30电子伏特动能的光电子和液滴光发射光谱法来量化基于水相非弹性散射的能量损失，具体方法是对一种典型的表面活性溶质进行光电离，并将结果与均匀分布的水性溶剂的结果进行比较。由此，我们确定了直接和准确测量水相电子结合能所需的一般≳17电子伏特的电子动能要求，而与界面浓度分布无关。此外，在电子动能从10电子伏特降至高于电离阈值几电子伏特的范围内，我们观察并量化了由表面活性溶质产生的光电子的较低散射程度，使得在低至几电子伏特的电子动能下，中度扭曲的表面活性溶质光发射峰仍可分辨。这些结果表明，与对均匀分布的溶液成分进行的类似实验形成鲜明对比，液滴光发射光谱法可用于探测接近电离阈值的界面表面活性溶质动力学和二向色性效应。此外，它们为水性环境中的低电子动能散射提供了新的见解，从而解决了这一关键能量范围内目前缺乏可靠实验数据的问题。
