Ultrafast 2D IR spectroscopy of the excess proton in liquid water.

Chemists have spent centuries trying to understand what acids look like at the molecular level. It's clear now that water molecules in the liquid accommodate extra protons. Less clear is whether the protons piggyback on individual water molecules (Eigen structure) or find shared accommodation between two at a time (Zundel structure). Thamer et al. acquired time-resolved vibrational spectra across an unusually broad span of the mid-infrared, allowing them to monitor stretches and bends at the same time. Their results imply a more prominent role for the Zundel structure than previously anticipated. Science , this issue p. [78][1] [1]: /lookup/doi/10.1126/science.aab3908