TY - EJOUR AU - Vinklarek, Ivo AU - Trippel, Sebastian AU - Belina, Michal AU - Blum, Luisa AU - Bromberger, Hubertus AU - Slavicek, Petr AU - Küpper, Jochen TI - Proton transfer and hydronium formation in ionized water IS - arXiv:2602.17505 M1 - PUBDB-2026-00564 M1 - arXiv:2602.17505 PY - 2026 N1 - Main manuscript - 4 figures, 8 pages; Supplementary materials - 31 figures, 29 pages AB - Aqueous radiation chemistry emerges through ultrafast proton transfer and ion-radical formation with unexplored energy-redistribution dynamics steering the subsequent reactions. We performed time-resolved disruptive probing on pure water dimer, \text(H<sub>2</sub>\textO)<sub>2</sub>, to disentangle the post-ionization reactions. Through kinetic-energy-resolved ion imaging, we unraveled the dynamics in the \text(H<sub>2</sub>\textO)<sub>2</sub><sup>+</sup> ground state: at low-energy ( ∼ 0.05 eV) ultrafast proton transfer ( ∼ 19 fs) is followed by \textH<sub>3</sub>\textO<sup>+</sup>+\textOH fragmentation ( ∼ 360 fs). At higher energies, proton transfer becomes hindered ( ∼ 60 fs) while the subsequent fragmentation becomes faster ( ∼ 210 fs), evolving into coupled dynamics ( > 0.15 eV, ∼ 100 fs). Moreover, we observed \text(H<sub>2</sub>\textO)<sub>2</sub><sup>+</sup> stabilization through a Zundel-like motif. This reveals how ion-radical formation in ionized hydrogen-bonded networks shapes reactivity in aqueous dynamics. LB - PUB:(DE-HGF)25 UR - https://bib-pubdb1.desy.de/record/645058 ER -