MASS-SELECTIVE ANION-ZEKE SPECTROSCOPY OF THE IODINE-WATER CLUSTER

Mass selected and high resolution anion-ZEKE spectra of I-(H2O) are pr esented. Linewidths as narrow as 3 cm(-1) have been observed for a res olution of the apparatus of 2 cm(-1) (maximum resolution 1.5 cm(-1)). From a first tentative assignment we deduce electronic and vibrational information about the neutral ground and the lowest electronic excite d states of the iodine-water cluster. The spectra exhibit the typical iodine spin-orbit splitting, two low frequency vibrational modes of 45 cm(-1) and 210 cm(-1) and a shift of the whole transition system of m ore than 3000 cm(-1). The latter is mainly due to the strong interacti on of the iodine anion with the water molecule. Rotational excitation is discussed. In addition, mass spectra of anionic iodine-water cluste rs (0 <n <18) are presented. There is no evidence for thermodynamicall y preferred cluster size.