We reexamined hydrated electron motifs in water cluster anions using photoelectron and electronic absorption spectroscopies under identical ion source conditions. The structural motifs, previously characterized as four, are now established as five in the present work, thereby refining the framework of hydrated electron isomers. Time-resolved photoelectron spectroscopy revealed motif-dependent relaxation dynamics, with certain surface-bound species undergoing more efficient excited-state autodetachment than others. Extending the temporal probing window uncovered long-lived vibrationally excited ground-state anions (τ ∼ 340 ps), far exceeding prior expectations, while increasing cluster size enhanced internal conversion efficiency. These results closely align with theoretical predictions. More broadly, they demonstrate that excited-state dynamics are highly sensitive to local structure, giving rise to distinct relaxation pathways under different hydration environments. The structure–dynamics relationships established here provide a foundation for extending such studies to other hydrated species, advancing fundamental insight into electron solvation and relaxation in aqueous systems. Hydrated electrons are expected to exhibit diverse structural motifs, however, the full framework of hydrated electron isomers remains underexplored. Here, the authors use photoelectron and electronic absorption spectroscopies to reexamine hydrated electron motifs in water cluster anions, reporting motif-dependent relaxation dynamics, with certain surface-bound species undergoing more efficient excited-state autodetachment than others.
An et al. (Sat,) studied this question.