Vibrational predissociation spectroscopy of Cs+(H2O)1−5

Abstract

Infrared spectra of Cs⁺(H₂O)₁₋₅ were obtained from vibrational predissociation of mass‐selected cluster ions in a triple quadrupole mass spectrometer using a pulsed‐tunable infrared laser in the 2.6–3.0 μm region. By comparison to size‐selective infrared spectra of neutral water clusters, the structure of hydrogen‐bonded water clusters complexed to the Cs⁺ can be observed for cluster ions with three or more water molecules. The onset of hydrogen bonding is also marked by the presence of structural isomers. There is also evidence for an unusual change in the vibrational transition moments for the symmetric and asymmetric O–H stretch, for isolated (non‐hydrogen‐bonded) water molecules, where the symmetric stretch is substantially enhanced.