As in most chemistry/physics papers, the true marvel is often not the actual phenomena being studied, but the observational techniques used to study those phenomena. In this case, it's by complexing the hydronium cluster with molecules that accept H-Bonds increasingly strongly, and then tracking the frequency of every O-D stretch vibration in the complex, as a hydron is incrementally pulled to a neighbouring water molecule.
As in most chemistry/physics papers, the true marvel is often not the actual phenomena being studied, but the observational techniques used to study those phenomena. In this case, it's by complexing the hydronium cluster with molecules that accept H-Bonds increasingly strongly, and then tracking the frequency of every O-D stretch vibration in the complex, as a hydron is incrementally pulled to a neighbouring water molecule.