Oxygen K-edge X-ray absorption spectroscopy (XAS) of an aqueous acetonitrile solution exhibited a sharp peak at approximately 537 eV, which was similar to that of water vapor and was not observed in liquid water. The inner-shell spectra of isolated water molecules and water clusters of different sizes surrounded by acetonitrile molecules were obtained by extracting these water structures from the liquid structures of aqueous acetonitrile solutions, as calculated using molecular dynamics simulations. The sharp peak profiles of the O K-edge XAS spectra were derived not from water clusters but from isolated water molecules surrounded by acetonitrile molecules. The present study proposes that isolated water molecules are easily formed in aqueous acetonitrile solutions and that the electronic structures of the isolated water molecules can be analyzed using O K-edge XAS spectra, which separates the contributions of small water clusters.

中文翻译：

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使用氧 K 边 X 射线吸收光谱探测乙腈水溶液中的分离水分子

乙腈水溶液的氧K边X射线吸收光谱（XAS）在约537 eV处呈现出尖峰，该尖峰与水蒸气的尖峰相似，并且在液态水中未观察到。通过从乙腈水溶液的液体结构中提取这些水结构，获得了乙腈分子包围的孤立水分子和不同尺寸的水簇的内壳光谱，并使用分子动力学模拟进行了计算。 O K 边 XAS 光谱的尖锐峰轮廓不是源自水簇，而是源自被乙腈分子包围的孤立水分子。本研究提出，在乙腈水溶液中很容易形成孤立的水分子，并且可以使用 O K 边 XAS 光谱分析孤立的水分子的电子结构，该光谱分离了小水簇的贡献。