Dissociations of water ions after valence and inner-valence ionization

Energy selected and mass-resolved electron-ion coincidence spectra of heavy water have been recorded for ionization energies from 18 to 35 eV. Dissociation from the B²B₂ state produces both O⁺ and D₂ ⁺ at energies near their thermodynamic thresholds in addition to the known products D⁺ and OD⁺. The relative yields of O⁺, OD⁺, and D⁺ in the B²B₂ state breakdown diagram are modulated by the vibrational structure of the B-state population, implying incomplete energy equilibration before fragmentation. Decay from the C-state produces OD⁺ in addition to the known O⁺ and D⁺. The fragment kinetic energies suggest that O⁺ and D⁺ from the C state are the products of full atomization of the molecule.