Electron stimulated ion desorption (ESD) is a highly sensitive tool for probing surface interactions, particularly in weakly coupled condensed matter. In this project, we have observed ion ejection from low temperature ice films supported on rare gas underlayers. Our measurements suggest that excitation of the rare gas underlayers can be transferred to water molecules at the interface, resulting in ion ejection. Measurements of protonated water cluster ejection have been made previously, where it was determined that the clusters are ejected by Coulomb explosion from a positively charged partner. ESD is known to eject fragments from water ice via multi-electron shake up resulting in 2-hole, 1-electron repulsive states. A 2-hole final state required for Coulomb explosion requires an Auger-type ejection of a secondary electron. Until now, our observations of Coulomb explosion have been explained by strictly inter-molecular electron reorganization. In the present study, transfer of energy occurs between partners that are bonded only by weak van der Waals interactions. This strongly suggests that energy transfer can occur between very weakly coupled species and fits well with the mechanism of Intermolecular Coulomb Decay (ICD) proposed by Santra and Cederbaum. This raises such question as: what is the lowest energy necessary for Coulomb explosion in the condensed phase? What are the relative efficiencies for ICD based on the intermolecular coupling? or based on electronic structure of the monomer units? Is this mechanism operational in low energy electron induced damage of DNA?
Water on Metal Oxides
Decomposition of water to form hydrogen and oxygen gasses using only solar photons as an energy source is of great interest to the renewable energy community. Zirconia (ZrO2) is known to produce hydrogen from water while under irradiation by gamma or ultra-violet photons. Additionally, zirconia is one of very few water splitting catalysts to function without the aid of an expensive co-catalyst (such as platinum). Research efforts in the Orlando group are focused on exploring zirconia's unique ability to split water without a co-catalyst in hopes of finding some unique property that can be adapted to systems that work in the visible spectrum.