Considering the off-diagonal elements of the Hamiltonian in Table , we indeed find that the Cav s and σ * OH orbitals are coupled by up to several eV, with the largest average coupling of 4.49 eV found for σ * 1 , which is also the closest OH bond to the electron. Similarly large couplings are seen for σ * 2 through σ * 4 , but by σ * 5 , the coupling has dropped to 0.33 eV. These values are consistent with the inner solvent shell of e - (aq) comprising four OH-aligned water molecules. The couplings may be viewed rather like Charge-Transfer (CT) integrals between the donor Cav s orbital and acceptor σ * OH orbitals. In this CT context, the large magnitude of the couplings can be understood as resulting from two aspects of e - (aq) . First, the diffuse nature of the Cav s orbital provides a high degree of spatial overlap with the acceptor σ * OH of the first solvent shell, which explains why the coupling drops off for the fifth and further σ * OH orbitals. Second, the transition density connecting the Cav s and σ * OH orbitals is localized near the partially positive H atoms (see Fig. ), which results in an attractive Coulombic coupling.