Dissociative photodetachment studies of O−(H2O)2, OH−(H2O)2, and the deuterated isotopomers: Energetics and three-body dissociation dynamics

Abstract

Photoelectron–photofragment coincidence spectroscopy was used to study dissociative photodetachment of the doubly hydrated clusters of oxide and hydroxide, M−(H2O)2→M+2H2O+e− (M=O, OH). These experiments yield information on the energetics of the parent anion and the dissociation dynamics of the photodetached neutral species. Photoelectron spectra and photoelectron–photofragment coincidence spectra are presented and compared to data for O−(H2O) and OH−(H2O). Unlike the singly hydrated species, no evidence of vibrationally resolved product translational energy distributions is observed. The second hydration energy of O− with both H2O and D2O was also measured to be 0.80±0.08 and 0.81±0.08 eV, respectively. The three-body dissociation dynamics of the neutral clusters produced by photodetachment were studied by measuring the velocities and recoil angles of all the particles in coincidence. The observed partitioning of momentum is consistent with a two-step mechanism or dissociation from a wide range of starting geometries.