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

Abstract

The dissociative photodetachment of O2−(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 O2−(H2O)1–2, permitting a determination of the first and second energies of hydration for O2− 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 O2−(H2O) and O2−(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: O2−(H2O)2+hν→O2+2H2O+e− is also reported. The observed partitioning of momentum is consistent with either a sequential dissociation or dissociation from a range of initial geometries.