PNNL

Abstract

Recently, water monomer dissociation energies from neutral water clusters were estimated from the measured appearance energies resulting from vacuum ultraviolet photoionization. The monomer dissociation energies of neutral water clusters were determined via a thermodynamic cycle, which encompassed the experimentally measured appearance energies of the photoionized water clusters and the previously reported dissociation energies of protonated water clusters. A key approximation was assumed - that the relaxation energy for the process ! (H2O)n + "(H2O)n -1H+ +OH• is zero. We will show that the relaxation energies are large and thus cannot be neglected. Thus, the neutral water cluster monomer dissociation energies cannot be determined directly from the measured ionization potentials since they are themselves involved in the thermodynamic cycle. This work was supported by the Division of Chemical Sciences, Geosciences and Biosciences, Office of Basic Energy Sciences, US Department of Energy. The Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy. Computer resources were provided by the Office of Science, US Department of Energy.