  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.
