Topology of the adiabatic potential energy surfaces for the resonance states of the water anion

The potential energy surfaces corresponding to the long-lived fixed-nuclei electron scattering resonances of H2O relevant to the dissociative electron attachment process are examined using a combination of ab initio scattering and bound-state calculations. These surfaces have a rich topology, characterized by three main features: a conical intersection between the (2)A(1) and B-2(2) Feshbach resonance states; charge-transfer behavior in the OH ((2)Pi)+H- asymptote of the B-2(1) and (2)A(1) resonances; and an inherent double-valuedness of the surface for the B-2(2) state the C-2v geometry, arising from a branch-point degeneracy with a B-2(2) shape resonance. In total, eight individual seams of degeneracy among these resonances are identified.