Infrared Spectroscopy of the Hydrated Electron Clusters (H₂O)n⁻, n = 6, 7:  Evidence for Hydrogen Bonding to the Excess Electron

We report the observation of strong vibrational resonances in the photodetachment spectra of (H 2 O) n -, n = 6, 7, clusters in the mid-infrared region. The resonances appear over a continuous background and occur in the spectral region corresponding to hydrogen bonding (∼3400 cm -1 ). On the basis of recent calculations by Kim et al. ( Phys. Rev. Lett. 1996, 76, 956), we assign these features to “free” OH groups interacting with the excess electron. This assignment is supported by the fact that excitation of the free OH vibration is observed in the photodetachment of (H 2 O) 6 - (Coe, et al. J. Chem. Phys . 1990, 92, 3980) indicating that the anion is distorted relative to the neutral along this coordinate.