Ionic Solutions Probed by Resonant Inelastic X-ray Scattering

Abstract

X-ray spectroscopy is a powerful tool to study the local charge distribution of chemical systems. Together with the liquid jet it becomes possible to probe chemical systems in their natural environment, the liquid phase. In this work, we present X-ray absorption (XA), X-ray emission (XE) and resonant inelastic X-ray scattering (RIXS) data of pure water and various salt solutions and show the possibilities these methods offer to elucidate the nature of ion-water interaction.

Cationic and Anionic Impact on the Electronic Structure of Liquid Water

“…X-ray spectroscopy allows measuring directly the electronic properties of a system and provides direct information about the local electronic structure around a specific element in a bulk chemical environment. [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] Previous soft X-ray absorption studies on aqueous solutions reported strong distortions of the pre-, main-and post edge of the X-ray absorption spectra on the oxygen K-edge in the vicinity of the ions. 7,30,31,33 These changes have been assigned to weakening and strengthening of the hydrogen bonds in the solvation shell around the cations.…”

“…27,35,36 Recently, several soft XES experiments have reported that the electronic properties of water is altered by the presence of salt ions only at high salt concentrations. 28,[37][38][39][40] However, the dominating change that is observed is an intensity decrease of the lower energy part of the split lone pair orbital peak in dependence of the concentration and the type of salt ions, which consisted mainly of Clas anion and various cations (NH 4 + , Li + , K + , Na + , Mg 2+ & Ca 2+ ). These changes were assigned to the distortion of the hydrogen bond network.…”

“…These changes were assigned to the distortion of the hydrogen bond network. 28,[37][38][39][40] The modification in the electronic properties were relatively small such that even at the highest concentration for monovalent (7M) and divalent (4M for CaCl 2 ) salt ions the splitting was still observed.…”

“…In experimental XE studies, noticeable distortion in the electronic properties of water is only observed at high salt concentration. 28,[37][38][39] Theoretical results show significant changes in the electronic properties of water molecules in proximity of the ions. For water molecules in the second solvation shell of the ion and beyond, the electronic properties of water show negligible distortions compared to bulk water.…”

Development of Ultrafast X-ray Free Electron Laser Tools in (Bio)Chemical Research

“…Life-relevant motions, however, can be as slow as seconds or even up to minutes' or hours' time scales. The origin of these time scale differences is based on the complexity of the coordination space of a proceeding reaction [8][9][10][11][12][13][14].…”