Spectrum and decay of the doubly charged water ion

Abstract

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.

Electron-impact ionization of the water molecule at large momentum transfer above the double-ionization threshold

“…Indeed, photoelectron spectroscopy [34][35][36] and EMS [37][38][39][40][41] have provided an excellent picture of the single ionization of water below the vertical double-ionization threshold (∼39 eV [42]). This has been complemented by years of assiduous effort devoted to studying the double ionization of this molecule, which have included Auger electron spectroscopy [43,44], photoion-photoion coincidence spectroscopy [45], double charge transfer spectroscopy [46], photoelectron-photoelectron coincidence spectroscopy [42], and electron-impact dissociative double-ionization crosssection measurements [47,48]. Nevertheless, to the best of our knowledge there have been no attempts to measure (e,2e) and (e,3-1e) spectra at large binding energies for this molecule, which may provide highly sensitive information on the correlated motion of electrons.…”

Fluorescence Emission of Excited Hydrogen Atoms after Core Excitation of Water Vapor

“…Because of the weak interaction of the spectator electron with the rest of the molecule, we consider the molecule to be left essentially in a doubly ionized state after the spectator decay. Theoretical and experimental studies of water dications in the gas phase indicate that all configurations are dissociative, and dissociation into OH H is the strongest channel [15,16]. Thus, we expect the water molecule to dissociate along one OH-H bond due to Coulomb repulsion.…”

Electron transfer reactions in collisions of low energy Neq+ (q=3–5) ions with CO2 and H2O molecules

“…(1) reduces to Q = E. In the present measurements, the translational energy spectra are expressed in terms of the Q-values and no correction was added to the measured energy gain. The energy levels for Ne q+ ions used in calculating the energy defect E were taken from Bashkin and Stoner [24] and other sources [25][26][27][28][29][30]. To identify the reaction channels involved, the energy spectra for Ne q+ (q = 3-5)-Ar collision systems [20] were used as a standard to calibrate the Q-scale for the spectra observed in the present work.…”