Electron Scattering and Electron Angular Anisotropy in Water and Aqueous Solution

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The project gives new insights into electron scattering mechanisms in liquid water and aqueous solutions and its impact on photoelectron angular distributions using photoelectron spectroscopy in international collaboration. Electron scattering is crucial for understanding energy deposition, radical formation, and biological damage by slow and fast electrons, and a correct interpretation of spectra from liquid water and aqueous solutions.In the past year, it was demonstrated that surface-active molecules (here: perfluoropentanoate) in aqueous solution can be precisely mapped using photoelectron angular distributions (PADs). Electron scattering alters the PAD signature in a way that is uniquely linked to the probing depth down to an Angstrom resolution. Combined with the chemical specificity of photoemission, this novel technique paves the way to study the detailed surface composition of solutions relevant for, e.g., atmospheric chemistry.Recent results reveal that electron scattering affects surface-active species differently than bulk species. Photoelectrons from the surface do not suffer from scattering in the bulk liquid, and are thus detectable down to much lower kinetic energies. This distinction is crucial to understand photoelectron spectra from low-energy sources such as lasers, which might be misinterpreted if the surface-propensity and concentration is not considered. These results are currently prepared for publication.Furthermore, a method for accessing the work function (surface potential) of aqueous solutions has been developed and is currently under review.