| Recent experimental and theoretical studies indicate that the gas-liquid interface can behave in distinct ways, providing its own medium for reaction and controlling entry into the bulk. Research in the Nathanson group has shown that this is true for gas phase DCl molecules reacting with pure and salty glycerol solutions, where a small fraction of the impinging DCl molecules undergo D→H exchange and desorb as HC1 in less than a microsecond, limiting this reaction to the near-interfacial region. The presence of this surprising interfacial exchange pathway in pure and salty glycerol solutions prompted us to ask whether a similar interfacial reaction pathway occurs in aqueous solutions.;In this thesis, we describe molecular beam scattering experiments that allow us to explore collisions of DCl molecules with aqueous solutions through the addition of LiBr to H2O, which lowers the freezing point below 212 K for the 7.5 m LiBr eutectic and reduces the vapor pressure to ∼5 mTorr. Most notably, we find no evidence of rapid, near-interfacial D→H exchange in the cold, salty solution. At low collision energies of 10 kJ mol -1, nearly all impinging DCl molecules become momentarily trapped at the surface. Approximately 10% of these thermalized molecules desorb immediately as intact DCl while the rest enter the solution, ionizing to Cl- and D+/H+. Roughly 2% of these dissolved ions recombine and evaporate as HC1 over our 0.12 s observation time, implying an average residence time of H+ and Cl- of at least 10 s.;The cold, salty water studies are experimentally challenging and imply that vapor pressures of 5-10 mTorr are the upper limit of the wetted-wheel technique. At these vapor pressures, ∼30% of the impinging HCl molecules collide with evaporating water molecules, limiting our ability to determine the uptake of gaseous HC1. This thesis also demonstrates how high vapor pressures distort time-of-flight spectra and develops ways to analyze scattering experiments using high vapor pressure liquids. |
