Negative-Ion/Positive-Ion Coincidence Yields of Core-Excited Water

We report yields of mass-resolved negative ions and positive ions measured in coincidence after core-excitation of water molecules. The analysis of negative-ion/positive-ion and negative-ion/positive-ion/positive-ion coincidence events provides new information on pathways leading to negative ion production, enhancing the present understanding of the dissociation processes of the water molecule. Dissociation following (resonant) Auger decay dominates negative ion production, but radiative decay is shown to contribute above the O 1s ionization threshold. A peak in the H-/O+ yield above the O 1s threshold is attributed to decay from doubly excited states.