Reaction Pathways of Water Dimer Following Single Ionization

Water dimer $({\text{H}}_2\text{O}{)}_2$ – a vital component of the earth’s atmosphere – is an important prototypical hydrogen-bonded system. It provides direct insight into fundamental chemical and biochemical processes, e.g., proton transfer and ionic supramolecular dynamics occurring in astro- and atmospheric chemistry. Exploiting a purified molecular beam of water dimer and multi-mass ion imaging, we report the simultaneous detection of all generated ion products of $({\text{H}}_2\text{O}{)}_2^{+}$-fragmentation following single ionization. Detailed information about ion yields and reaction energetics of 13 ion-radical pathways, 6 of which are new, of $({\text{H}}_2\text{O}{)}_2^{+}$ are presented, including strong ${}^{18}\text{O}$-isotope effects.