We next consider how many water O1s orbitals contribute to the 533 eV peak. This is analyzed in Fig. , which shows a scatter plot of the excitation energies and oscillator strengths versus distance of the SOMO centroid from the O1s hole for the cavity transitions identified above. A clear trend of increasing excitation energy with increasing e --oxygen distance is observed. This can be understood as reflecting the Coulomb penalty of creating a separated p-h pair following O1s-to-cavity excitation. In contrast to the increase in en-ergy, the oscillator strength is seen to dramatically decrease with e --oxygen distance, which is consistent with our previous finding that σ * OH occupation by the excess electron drops rapidly with distance. As a result, the 533 eV feature is dominated by transitions from O1s orbitals within 3.3 Å of the excess electron, i.e. its first solvation shell. 24 e (aq) Å Finally, we seek to quantify the influence of Coulomb repulsion from the excess electron on the energy of the cavity XAS transitions, i.e. how valid is a one-electron picture of the transition? We thus re-computed XAS energies of e - (aq) configurations after removing the excess electron, i.e. an overall charge neutral system. Supporting a oneelectron picture, we find the neutral XAS transitions occur at essentially the same energy as the anionic transitions (see Fig. ).