Ions and Surfactants at Aqueous Solution-Vapor Interfaces Investigated with Photoelectron Spectroscopy

Aqueous solution-vapor interfaces govern important phenomena in the environment and atmosphere, including the uptake and release of trace gases by aerosols and CO₂ sequestration by the oceans. Surfactants are omnipresent on aqueous surfaces exposed to the atmosphere and can potentially alter the propensity of dissolved ions, such as Na⁺, Mg⁺, Ca²⁺, and Cl^–, for the interface through direct interactions between their functional groups (e.g., -COO^–, -NH3⁺) with the ions. The increased propensity of ions for the aqueous solution-air interface in the presence of  surfactants might also increase their availability as reactants in heterogeneous chemical reactions with trace gases in the atmosphere. While field and reactor studies have provided a wealth of information on the general chemical composition of, e.g., the ocean-air interface, detailed molecular-scale information on the mutual effects of ions and surfactants is still relatively scarce. This talk will discuss opportunities and challenges for investigations of liquid-vapor interfaces using X-ray photoelectron spectroscopy and describe recent investigations of the interaction of ions and surfactants at the liquid-vapor interface of artificial seawater solutions.