Impact of anion polarizability on ion pairing in microhydrated salt clusters.

Despite longstanding interest in the mechanism of salt dissolution in aqueous media, a molecular level understanding remains incomplete. Here, cryogenic ion trap vibrational action spectroscopy is combined with electronic structure calculations to track salt hydration in a gas phase model system one water molecule at a time. The infrared photodissociation spectra of microhydrated lithium dihalide anions [LiXX'(HO) ] (XX' = I, ClI and Cl; = 1-3) in the OH stretching region (3800-2800 cm) provide a detailed picture of how anion polarizability influences the competition among ion-ion, ion-water and water-water interactions.