The observation of electron induced vibrational redshifts and a significant enhancement of coupling to water's OH stretch compared to MQC results suggests that the excess electron interacts with water much more intimately than simple electrostatics would suggest. The vibrational redshifts arise from occupation of σ * OH orbitals, the energy of which is strongly modulated by the OH stretch mode. It is thus reasonable to expect that σ * OH occupation also explains the enhanced coupling between the electron and stretch modes. To explore this further, in the next section we seek to quantify the occupation of σ * OH orbitals, using NBO analysis.