VIBRATIONAL-SPECTRUM OF I-(H2O)

The infrared spectrum of the ionic cluster I- (H2O) was recorded from 3170 to 3800 cm(-1) by vibrational predissociation spectroscopy. A str ong multiplet observed at 3415 cm(-1) and a narrow band at 3710 cm(-1) were assigned as a hydrogen-bonded OH stretch and free OH stretch res pectively, indicating that H2O forms a single hydrogen bond with the i odide anion. Ab initio vibrational frequencies and intensities were co mputed at the second-order Moller-Plesset (MP2) level for the minimum energy configuration, a nearly linear hydrogen-bonded isomer, and for a low-lying saddlepoint, a symmetric C-2v bridged isomer. The spectrum predicted for the hydrogen-bonded isomer agreed well with experiment.