Photoelectron spectra of hydrated electron clusters vs. cluster size:: connecting to bulk

Connecting cluster properties to bulk can result in new insights, both for the bulk and for clusters, and this is especially the case for the hydrated electron, e(-)(aq), and its cluster counterparts. In bulk, e(-)(aq) can be viewed as an anionic defect state of pure water, which is itself a large-band-gap semiconductor. Thus, when properly extrapolated to bulk, the properties of (H2O)(n)(-) clusters must reflect important energetic properties of bulk water. Several of these have been extracted and are presented here. As for the nature of (H2O)(n)(-) clusters themselves, the topic has now inspired spirited debate for over two decades. Here, we offer our perspective on these intriguing entities. Among several isomeric groups of (H2O)(n)(-) and (D2O)(n)(-) clusters, the one having the highest electron binding energies (herein called bulk embryonts) has been extrapolated to deduce the implied photoelectron spectrum of the bulk hydrated electron. The legitimacy of the lineshape fitting procedures used here is supported by the successful extrapolation of cluster absorption data to its known bulk benchmarks.