H+2 formation from H2O+ mediated by the core-excitation-induced nuclear motion in H2O

The vibrational structure of the O 1s^-12b₂ core-excited state of H₂O is observed and ascribed to the mixture of symmetric stretching and bending motions with a₁ symmetry. The formation of H⁺₂ is found to increase linearly with an increase in energy stored in the nuclear motion of the O 1s^-12b₂ state, demonstrating that this dissociation channel is mediated by the nuclear motion in the core-excited state. The reaction pathway to the H⁺₂ formation along the Auger final state of H₂O⁺, mediated by the nuclear motion before the Auger decay, is discussed with the help of ab initio potential surfaces of the Auger final states.