Ion hydration studied by x-ray Compton scattering

We present an x-ray Compton scattering study on aqueous lithium chloride as a function of concentration, ranging from dilute solutions to saturation. The experimental observations are analyzed by simulations based on model cluster calculations within the density functional theory. The Compton scattering technique is found to be sensitive predominantly to the ion-ion and ion-oxygen bond-length distributions as well as to the hydration number and ion pairing. We explain the concentration-induced changes in the ground-state electron momentum densities by formation of hydration shells around the ions, providing upper limits for the average ion-oxygen bond lengths. In particular, this study provides stringent constraints on the hydration shells of chloride ions.