Energetics and dissociative photodetachment dynamics of superoxide-water clusters:: O2-(H2O)n, n=1-6

The dissociative photodetachment of O-2(-)(H2O)(n=1-6) was studied at 388 and 258 nm using photoelectron-multiple-photofragment coincidence spectroscopy. Photoelectron spectra for the series indicate a significant change in the energetics of sequential solvation beyond the fourth water of hydration. Photoelectron-photofragment kinetic energy correlation spectra were also obtained for O-2(-)(H2O)(1-2), permitting a determination of the first and second energies of hydration for O-2(-) to be 0.85 +/-0.05 and 0.70 +/-0.05 eV, respectively. The correlation spectra show that the peak photofragment kinetic energy release in the dissociative photodetachment of O-2(-)(H2O) and O-2(-)(H2O)(2) are 0.12 and 0.25 eV, respectively, independent of the photon and photoelectron kinetic energies. The molecular frame differential cross section for the three-body dissociative photodetachment: O-2(-)(H2O)(2) + h nu -->O-2 + 2H(2)O + e(-) is also reported. The observed partitioning of momentum is consistent with either a sequential dissociation or dissociation from a range of initial geometries. (C) 2001 American Institute of Physics.