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In this paper, we examine decay and fragmentation of core-excited and core-ionized water molecules combining quantum chemical calculations and electron-energy-resolved electron-ion coincidence spectroscopy. The experimental technique allows us to connect electronic decay from core-excited states, electronic transitions between ionic states, and dissociation of the molecular ion. To this end, we calculate the minimum energy dissociation path of the core-excited molecule and the potential energy surfaces of the molecular ion. Our measurements highlight the role of ultra-fast nuclear motion in the 1a 1 -1 4a 1 core-excited molecule in the production of fragment ions. OH + fragments dominate for spectator Auger decay. Complete atomization after sequential fragmentation is also evident through detection of slow H + fragments. Additional measurements of the non-resonant Auger decay of the core-ionized molecule (1a 1 -1 ) to the lower-energy dication states show that the formation of the OH + + H + ion pair dominates, whereas sequential fragmentation OH + + H + → O + H + + H + is observed for transitions to higher dication states, supporting previous theoretical investigations.

The solvation of alkali-halides in water clusters at nanoscale is studied by photoelectron spectroscopy using synchrotron radiation. The Na 2p, K 3p, Cl 2p, Br 3d, and I 4d core level binding energies have been measured for salt-containing water clusters. The results have been compared to those of alkali halide clusters and the dilute aqueous salt solutions. It is found that the alkali halides dissolve in small water clusters as ions.