H2+formation fromH2O+mediated by the core-excitation-induced nuclear motion inH2O

Abstract

The vibrational structure of the $\mathrm{O} {1s}^{\ensuremath{-}1}{2b}_{2}$ core-excited state of ${\mathrm{H}}_{2}\mathrm{O}$ is observed and ascribed to the mixture of symmetric stretching and bending motions with ${a}_{1}$ symmetry. The formation of ${\mathrm{H}}_{2}^{+}$ is found to increase linearly with an increase in energy stored in the nuclear motion of the $\mathrm{O} {1s}^{\ensuremath{-}1}{2b}_{2}$ state, demonstrating that this dissociation channel is mediated by the nuclear motion in the core-excited state. The reaction pathway to the ${\mathrm{H}}_{2}^{+}$ formation along the Auger final state of ${\mathrm{H}}_{2}{\mathrm{O}}^{+},$ mediated by the nuclear motion before the Auger decay, is discussed with the help of ab initio potential surfaces of the Auger final states.