Photoelectron spectroscopy of the `missingʹ hydrated electron clusters (H2O)−n, n=3, 5, 8 and 9: Isomers and continuity with the dominant clusters n=6, 7 and ⩾11

We report photoelectron spectra for the small anionic water clusters, W−n (n=2–11, excluding the tetramer), to explore the nature of the trace species surrounding the intense parents appearing at magic numbers n=2, 6, 7 and ⩾11. Two isomeric forms are observed for most of these anions, which are distinguishable by their vertical electron detachment energies (VDE). While the band corresponding to the more strongly bound form continuously evolves from the band characteristic of the larger (n⩾11) clusters, the smaller clusters display a dramatically smaller sequential solvation shift, resulting in a sharp break in the cluster radius (∝n1/3) dependence of the VDEs.