Abstract
Acid-base reactions are among the most important chemical processes in aqueous solution, but it is very difficult to characterize the solvated ions that are involved, especially the solvated proton. In his Perspective, Zwier discusses reports by Shin et al. and Miyazaki et al. in the same issue that reveal details of the structure of protonated water by means of infrared spectroscopy. The infrared spectra of a series of protonated water clusters H(HO)with n = 6 to 27 shed new light and raise new questions about the nature of the proton in water, its position in the finite-sized cluster (surface or interior), and the structure of the cluster in the size region of the proposed dodecahedral cage (n = 21).