Molecular Beam Scattering from Flat Liquid Jets: Exploring Dynamics at the Aqueous Interface

Gas–liquid surface interactions represent the critical first steps in adsorption, dissolution, and unique interfacial reactions. Multiphase chemistry on aqueous surfaces is especially prevalent, driving processes from atmospheric carbon cycling to industrial catalysis. Molecular beam scattering experiments employing novel flat liquid jet techniques offer a powerful probe into the fundamental dynamics and mechanisms of gas-phase particles colliding with a liquid surface.^1–3

Here we present the first translational energy distributions of molecular beams such as He, Ne, Ar, CD₄, and ND₃ scattered from a flat jet of cold salty water, collected through a range of deflection angles and analyzed with kinematic modeling. We find that the aqueous interface facilitates a high degree of collisional energy transfer compared to hydrocarbon surfaces, consistent with observed super-specular scattering patterns. Different gaseous species exhibit variations in scattering behavior, with ND₃ appearing to undergo complete surface trapping. Interactions between He and the liquid surface are weak, allowing He scattering to serve as a probe for surface roughness.