Dissociative electron attachment to the hydrogen-bound OH in water dimer through the lowest anionic Feshbach...

The lowest energy Feshbach resonance state of the water dimer anion is computationally studied as the hydrogen-bonded OH moiety is stretched from its equilibrium position toward the hydrogen bond acceptor. The purpose is to treat a simple model system to gain insight into how hydrogen bonding may affect dissociative electron attachment to water in condensed phases. In the case of a water monomer anion, the analogous potential surface is known to be repulsive, leading directly to dissociation of H(-). In contrast, in the dimer anion, a barrier is found to dissociation of the hydrogen-bonded OH moiety such that the migrating hydrogen can be held near the Franck-Condon region in a quasibound vibrational state for a time long compared to the OH vibrational period. This behavior is found both for the case of an icelike dimer structure and for a substantial majority of liquidlike dimer structures. These findings raise the possibility that due to effects of hydrogen bonding, a molecule-centered anionic entity that is metastable both to electron detachment and to bond dissociation may live long enough to be considered as a species in the radiolysis of condensed water phases.