Water Solvation Properties: An Experimental and Theoretical Investigation of Salt Solutions at Finite Dilution

Our combined analysis of first-principle simulations and experiments conducted on salt solutions at finite dilution shows that the high frequency range of the infrared spectrum of an aqueous solution of NaCl displays a shift toward higher frequencies of the stretching band with respect to pure water. We ascribe this effect to a lowering of the molecular dipole moments due to a decrease in the dipole moments of molecules belonging to the first and second solvation shells with respect to bulk water. An analysis of the dipole orientation correlations proves that the screening of solutes is dominated by short-range effects. These jointly experimental and theoretical results are corroborated by the good agreement between calculated and measured dielectric constants of our target solution.