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arXiv · 2602.17505

Proton transfer and hydronium formation in ionized water

Ivo S. Vinklárek·Sebastian Trippel·Michal Belina·Luisa Blum·Hubertus Bromberger·Petr Slavíček·Jochen Küpper
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Abstract

Aqueous radiation chemistry emerges through ultrafast proton transfer and ion-radical formation with unexplored energy-redistribution dynamics steering the subsequent reactions. We performed a time-resolved disruptive-probing experiment on pure water dimer, (H$_2$O)$_2$, to disentangle the elementary post-ionization reactions. Through kinetic-energy-resolved ion imaging, we unraveled the dynamics in the (H$_2$O)$_2^+$ ground state: at low-energy ($\sim$0.05~eV) ultrafast proton transfer ($\sim$19~fs) is followed by H$_3$O$^+$+OH fragmentation ($\sim$360~fs). At higher energies, proton transfer becomes hindered ($\sim$60~fs) while the subsequent fragmentation becomes faster ($\sim$210~fs), eventually ($>0.15$~eV) merging into coupled dynamics ($\sim$100~fs). Additionally, we observed H$_2$O)$_2^+$ stabilization proceeding through a Zundel-like structure. These timescales and product energies reveal how ion-radical formation in ionized hydrogen-bonded networks shapes reactivity in aqueous dynamics.

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Ivo S. Vinklárek, Sebastian Trippel, Michal Belina, Luisa Blum, Hubertus Bromberger, Petr Slavíček, Jochen Küpper. 2026-02-19. Proton transfer and hydronium formation in ionized water. https://arxiv.org/abs/2602.17505

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