The Influence of Water Molecules on the π* Shape Resonances of the Thymine Anion

Low-energy electrons have been shown to resonantly attach to DNA, inducing strand breakages and other damaging lesions. While computational studies have suggested that the nucleobase moieties can serve as the initial attachment site, there remains ambiguity over the exact character of the temporary anion resonances that form due to the unestablished role of the surrounding environment. Here, we investigate the influence of an aqueous environment on the low-lying anion shape resonances of the π* character of the thymine anion by applying frequency-resolved photoelectron spectroscopy to thymine-water cluster anions, T^-(H₂O)_n, with an increasing degree of hydration, n. Our results indicate that spontaneous solvent rearrangement will stabilize the π₂* and π₃* states into bound electronic states, and we observe evidence for internal conversion to the anion ground state, further aiding long-term electron capture via these resonances.