Effects of Cations on the Hydrogen Bond Network of Liquid Water: New Results from X-ray Absorption Spectroscopy of Liquid Microjets

The oxygen K-edge absorption spectra (XAS) of aqueous chloride solutions are measured for Li⁺, Na⁺, K⁺, NH⁺, C(NH2)₃⁺, Mg²⁺ and Ca²⁺ and 4 M cation concentrations. Density functional theory calculation have indicated that the ion-specific spectral variations arise from direct electronic perturbation of the unoccupied orbitals due to the presence of the ions, as a result of differences in charge transfer from the water molecules onto the divalent cations