Comparing QM/MM to MQC results (solid black and dashed red curves of Fig. tion); in particular, agreement is seen with the bend and asymmetric stretch at 1865 and 3665 cm -1 respectively. On the other hand, the e - (aq) QM/MM peaks are red shifted compared to the corresponding pure water frequencies at the FlexiBLE BH&HLYP-D3/6-31+G* QM/MM level (solid curve in panel (b)). The magnitudes of these excess electron-induced red shifts match very well with those seen in the experimental RR of e - (aq) : 72 50(∼30) cm -1 for the bend and 190(200) cm -1 for the stretch, with experimental numbers in brackets. The RR vibrational red shifts have been previously assigned to occupation of water's OH antibonding orbitals (σ * OH ) by the excess electron, which we confirm below.