An infrared study of the competition between hydrogen-bond networking and ionic solvation: Halide-dependent distortions of the water trimer in the X-center dot(H2O)(3), (X = Cl, Br, I) systems

Vibrational spectra of the water trimers solvating the halide anions (Cl-, Br-, I-) have been acquired in the OH stretching region by predissociation spectroscopy of the X- .(H2O)(3). Ar-3 complexes. These "wet" ions display two groups of bands assigned to normal modes of the (C-3) pyramidal structu re. We interpret the evolution of the spectra down the halogens in the cont ext of the rings closing up toward the structure of the bare (H2O)(3) neutr al. This trend is discussed in terms of the disruptive effect of the ionic H bonds on the water network. (C) 1999 American Institute of Physics. [S002 1-9606(99)02115-7].