Spectrum and decay of the doubly charged water ion

This is the authors' abstract. We don't add key points for this paper.

Ion–ion coincidence measurements on H2O, HDO, and D2O ionized by Heii light show that the main ion-pair dissociations from low-lying states of H2O2+ lead to OH++H+ and H++H++O. Distinct states of H2O2+ are deduced to be at 36.5±1 and at 42±1 eV above the H2O ground state. Double charge transfer measurements show two sets of singlet states of H2O2+ at 41.4 and 45 eV in agreement with the Auger spectrum. New ab initio calculations predict a vertical appearance energy of 39.2 eV for the H2O2+ ion in its 3B1 ground state, but show a very strong geometry dependence, and give an adiabatic value near 36.3 eV, in agreement with experiment.