1 . The result is shown in Table . As expected, the Cav s orbital has the highest population; however, σ * OH orbitals contribute an appreciable ∼0.3 e in total. In fact, the Cav s and five σ * OH orbitals sum to a population of 0.97 e, and thus together describe the excess electron's SOMO orbital almost in its entirety. The remaining amplitude of the SOMO is made up of contributions from lower-populated σ * OH orbitals and water Rydberg orbitals. This analysis is in qualitative agreement with the picture of excess electron binding in cavity-containing water cluster anions. In particular, Herbert and Jacobson noted that only ∼0.5 e of excess charge density is localized in the cavity of the idealized (H 2 O) - 24 cluster, with the remainder penetrating into the second solvation shell and beyond. Using a QM/MM model, Uhlig, Marsalek, and Jungwirth (UMJ) confirmed this picture extends to the condensed-phase e - (aq) and assigned 0.41 e of the excess charge to the cavity region, 0.24 e to a region overlapping with the first two solvation shells water molecules, and 0.35 e to a diffuse tail extending beyond the second solvation shell. We assign a larger contribution to a cavity state than UMJ, since the Cav s NBO also contains the diffuse tails that UMJ assigned separately. Our analysis provides additional quantitative insight into how the excess electron is able to have appreciable amplitude in the first two solvation shells, which is by populating the σ * OH orbitals.