Anion ZEKE-spectroscopy of the weakly bound iodine water complex

Zero kinetic electron energy photodetachment spectroscopy of I ^-•H₂O and I^-•D₂O has been performed from 27 660 to 28 500 cm^-1 and from 27 660 to 35 900 cm^-1, respectively. The I^-•D₂O spectral data and theoretical studies resulted in a reassignment of earlier anion-ZEKE spectra of iodide water (Bässmann, C.; et al. Int. J. Mass Spectrom. Ion Processes 1996, 159, 153). In opposite to the I^-•H₂O, the I^-•D₂O spectrum reveals a regular progression of the iodine-water van der Waals stretching mode and a short progression of even quanta of the van der Waals rocking mode. A rough estimation delivers dissociation thresholds of the anionic and of the lower and the upper spin-orbit component of the neutral van der Waals complex. A high resolution ZEKE spectrum of the van der Waals stretching mode (v = 1) reveals significant fine structure, which is found again in a former photodissociation spectrum of the anionic complex (Ayotte, P.; et al. J. Phys. Chem. A 1998, 102, 3067). Our assignments are supported by theoretical calculations of molecular structures and vibrational motions. Vibrational frequencies and isotope effects are reproduced very satisfyingly by these calculations.