Electron-initiated chemistry at the ambient water/air interface

Abstract The interaction of molecules with slow electrons can lead to profound chemical changes. So far, experimental probing of such interactions has been possible only with target systems in vacuum or in high energy environments where a range of processes and by-products can interfere with the electron-induced processes (e.g. in plasmas). Here, we demonstrate a method to cleanly deposit low-energy electrons onto an ambient water–air interface, with sufficient efficiency that its chemistry might be measured. Electrons are produced via the photoelectric effect at a photocathode and are driven onto an ambient water–air surface, to an anode. In traditional dissociation attachment experiments, high energy (> 10's eV) electrons excite water and oxygen molecules, leading to the detachment of secondary electrons. Monte Carlo simulations with homogeneous fields reveal that even with voltages tenfold of those used here, electrons > 2 eV are highly unlikely. This regime is similar to that of secondary electrons in traditional dissociative attachment experiments, which are those responsible for the observed electron-initiated chemistry. We follow the electron-initiated chemistry over time with a terephthalic acid dosimeter, which allows us to detect the presence of reactive products (OH•, e (aq) – ) using in-situ fluorescence spectroscopy. Graphical abstract