Isolation and Infrared Spectroscopic Characterization of Hemibonded Water Dimer Cation in Superfluid Helium Nanodroplets.

The structure of the minimum unit of the radical cationic water clusters, the (HO) dimer, has attracted much attention because of its importance for the radiation chemistry of water. Previous spectroscopic studies indicated that the dimers have a proton-transferred structure (HO·OH), though the alternate metastable hemibonded structure (HO·OH) was also predicted based on theoretical calculations. Here, we produce (HO) dimers in superfluid helium nanodroplets and study their infrared spectra in the range of OH stretching vibrations.