TY  - JOUR
AU  - Schnorr, Kirsten
AU  - Belina, Michal
AU  - Augustin, Sven
AU  - Lindenblatt, Hannes
AU  - Liu, Yifan
AU  - Meister, Severin
AU  - Pfeifer, Thomas
AU  - Schmid, Georg
AU  - Treusch, Rolf
AU  - Trost, Florian
AU  - Slavicek, Petr
AU  - Moshammer, Robert
TI  - Direct tracking of ultrafast proton transfer in water dimers
JO  - Science advances
VL  - 9
IS  - 28
SN  - 2375-2548
CY  - Washington, DC [u.a.]
PB  - Assoc.
M1  - PUBDB-2023-07219
SP  - eadg7864
PY  - 2023
AB  - Upon ionization, water forms a highly acidic radical cation H<sub>2</sub>O<sup>+</sup>· that undergoes ultrafast proton transfer (PT)—a pivotal step in water radiation chemistry, initiating the production of reactive H<sub>3</sub>O<sup>+</sup>, OH radicals, and a (hydrated) electron. Until recently, the time scales, mechanisms, and state-dependent reactivity of ultrafast PT could not be directly traced. Here, we investigate PT in water dimers using time-resolved ion coincidence spectroscopy applying a free-electron laser. An extreme ultraviolet (XUV) pump photon initiates PT, and only dimers that have undergone PT at the instance of the ionizing XUV probe photon result in distinct H<sub>3</sub>O<sup>+</sup> + OH<sup>+</sup> pairs. By tracking the delay-dependent yield and kinetic energy release of these ion pairs, we measure a PT time of (55 ± 20) femtoseconds and image the geometrical rearrangement of the dimer cations during and after PT. Our direct measurement shows good agreement with nonadiabatic dynamics simulations for the initial PT and allows us to benchmark nonadiabatic theory. 
LB  - PUB:(DE-HGF)16
C6  - 37436977
UR  - <Go to ISI:>//WOS:001033220400010
DO  - DOI:10.1126/sciadv.adg7864
UR  - https://bib-pubdb1.desy.de/record/599195
ER  -