Direct tracking of ultrafast proton transfer in water dimers

• DOI: 10.1126/sciadv.adg7864
• Publication Date: 2023-07-12T17:58:38Z
• Authors: Kirsten Schnorr; Michal Belina; Sven Augustin; Hannes Lindenblatt; Yifan Liu; Severin Meister; Thomas Pfeifer; Georg Schmid; Rolf Treusch; Florian Trost; Petr Slavíček; Robert Moshammer
• Keywords: Tracking (education)

Upon ionization, water forms a highly acidic radical cation H2O+· that undergoes ultrafast proton transfer (PT)-a pivotal step in radiation chemistry, initiating the production of reactive H3O+, OH[Formula: see text] radicals, and (hydrated) electron. Until recently, time scales, mechanisms, state-dependent reactivity PT could not be directly traced. Here, we investigate dimers using time-resolved ion coincidence spectroscopy applying free-electron laser. An extreme ultraviolet (XUV) pump photon initiates PT, only have undergone at instance ionizing XUV probe result distinct H3O+ + OH+ pairs. By tracking delay-dependent yield kinetic energy release these pairs, measure (55 ± 20) femtoseconds image geometrical rearrangement dimer cations during after PT. Our direct measurement shows good agreement with nonadiabatic dynamics simulations for initial allows us to benchmark theory.