Abstract The interaction of an ion with surrounding solvent molecules is revealed by X-ray absorption spectroscopy in transmission mode for the case of calcium dication dissolved in pure water, methanol and ethanol at the Ca K and L2,3-edges. The near-threshold K-shell excitation leads to two distinct solvent-dependent features, the Ca 1s to 3d and 4p electronic transitions, clearly indicating the ligand field decreases as water is changed to methanol and methanol to ethanol. On the other hand, the Ca L2,3-edge excitation leads to small changes in the absorption spectra and the peak assignment – mostly in terms of Ca 2p to eg and t2g transitions for each of the two spin orbit components – is strongly depending on the geometry of the first solvation shell around the dication and on the magnitude of the ligand-field multiplet effects. Our interpretation is supported by ab-initio quantum chemical calculations of the solvent dependence of chemical shifts for the Ca 3d and 4p unoccupied levels of the 1s and 2p excited states, performed on a small cluster including the nearest neighbor solvent molecules surrounding the Ca dication assuming a cubic (8-fold) solvent coordination.

中文翻译：

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利用 K 和 L2,3-边 X 射线吸收光谱法研究纯水、甲醇和乙醇溶液中溶剂化钙二阳离子结构

摘要 对于溶解在纯水、甲醇和乙醇中的钙二阳离子在 Ca K 和 L2,3 边缘的情况，通过 X 射线吸收光谱在透射模式下揭示了离子与周围溶剂分子的相互作用。接近阈值的 K 壳激发导致两种不同的溶剂相关特征，即 Ca 1s 到 3d 和 4p 电子跃迁，清楚地表明配体场随着水变为甲醇和甲醇变为乙醇而减小。另一方面，Ca L2,3-edge 激发导致吸收光谱和峰值分配的微小变化 - 主要是根据两个自旋轨道分量中的每一个的 Ca 2p 到 eg 和 t2g 跃迁 - 强烈取决于dication 周围的第一个溶剂化壳的几何形状和配体场多重效应的大小。