Selective negative-ion formation from core-valence doubly excited states of the water molecule

This study focuses on the role of negative-ion formation in the decay of core-valence doubly excited water molecules. Combining negative- and positive-ion coincidence measurements with calculated energies of core-valence doubly excited states, we find that O- and H- production is enhanced selectively. In particular, we suggest that O- production is correlated to double occupancy of the antibonding 4a1 virtual orbital, while H- appears at electronic states with double occupancy in 2b2. We also show that H- and O- can be created as a result of electron recapture close to the O 1s ionization potential.