Electron Attachment-Induced Shape Resonances in AT Base Pairs

In this work, we investigated the influence of base pairing and π-π stacking interactions on electron attachment-induced shape resonances in the adenine-thymine (AT) base pair. Resonance positions and widths are computed using a DLPNO-based equation of motion coupled-cluster approach in conjunction with the Padé analytical continuation method. Seven π*-shape resonances are identified for both linear and stacked AT geometries, consistent with the total number of resonances in isolated adenine and thymine. Natural orbital analysis reveals that low-energy resonances exhibit significant electron density delocalization over both nucleobases. This delocalization is enhanced in the stacked geometry, leading to appreciable stabilization and increased lifetimes of the resonance states. These results highlight the important role of intermolecular interactions in modulating electron attachment processes in DNA.