The potential energy surface corresponding the complex resonance energy of the 2B1 Feshbach resonance state of the water anion is constructed in its full dimensionality. Complex Kohn variational scattering calculations are used to compute the resonance width, while large-scale Configuration Interaction calculations are used to compute the resonance energy. Near the equilibrium geometry, an accompanying ground state potential surface is constructed from Configuration Interaction calculations that treat correlation at a level similar to that used in the calculations on the anion.
