The O K-edge XAS spectrum of pNA is even more featureless than the N K-edge XAS spectrum and compares well with experimental spectrum from Ref. 92. The XAS spectrum has a dominant feature at 531.1 eV originating from the XA 1 → c1B 2 transition, characterized by a a 1 → b 2 orbital transition with a delocalized π * particle orbital and the core hole delocalized on both the oxygen atoms (see the raw data in Table and NTO analysis in Table in the SI). This transition, along with the degenerate XA 1 → c1A 2 transition, is also dominant in the CVS-0 spectrum, but quenched in the CVS-uS spectrum. These two transitions have the same characteristic π * particle orbital, with the hole orbitals different (one is the symmetric and the other the antisymmetric combination of the oxygen 1s orbitals). Similar to the N K-edge CVS-uS spectrum, the O K-edge CVS-uS spectrum is dominated by fully symmetric transitions. In this case, the dominant transitions are XA 1 → c6A 1 , XA 1 → c7A 1 , and XA 1 → c1A 1 at 538.1 eV, 538.8 eV, and 536.2 eV, respectively. Whereas the first two transitions feature particle orbitals delocalized on the entire molecule, the third transition features a particle orbital that is largely localized at the nitro end of pNA. For details on the NTOs involved in the smaller features, we refer to the tabulated raw data used to construct the spectra shown in Figure and the corresponding NTO analyses in the SI.