pNA has a large dipole moment and features many charge-transfer valence excitations. The computed C K-edge XAS spectrum is comparable with the experimental spectrum in Ref. 92, although experimental features, except the ones around 285.0 eV and 287.5 eV and the shoulder around 286.0 eV, are not well differentiated. The dominant feature computed around 285.0 eV originates from the XA 1 → c1B 2 and XA 1 → c2B 2 transitions, both of 1s C → π * character. The former transition is characterized by b 1 → a 2 and a 1 → b 2 orbital transitions with the core hole delocalized over the two carbons at the meta position relative to the nitro group (see the raw data in Table and NTO analysis in Table in the SI). The latter tran-sition is characterised by a b 1 → a 2 with the core hole delocalized over the two carbons at the meta position relative to the amine group. The next two features, one at ≈ 285.9 and the other at at 286.5 eV, arise from the XA 1 → c3B 2 and XA 1 → c5B 2 transitions, respectively. The first one is a signature of the 1s → π * from the carbon atom bearing the nitro-group. The second, also of 1s → π * type, is a a 1 → b 2 transition with the core hole originating primarily from the C atom bearing the amino group, with some delocalization over the two nearest carbons. The computed XAS spectrum has a few other relatively intense features such as the XA 1 → c1B 1 at 287.0 eV, XA 1 → c7B 2 at 288.2 eV, XA 1 → c13A 1 at 289.5 eV, XA 1 → c11B 2 at 289.5 eV, XA 1 → c15B 1 at 290.1 eV, and XA 1 → c20A 1 at 290.3 eV. Their character (π * , σ * , Rydberg) becomes apparent upon inspecting the compilation of NTOs in Table in the SI.