Abstract. The reactive uptake of HOBr onto aqueous solutions containing CI' and Br-has been studied using a wetted-wall flow tube reactor. The uptake was found to be limited by

The reactive uptake of ClNO2 on pure water, NaBr, and mixed NaBr/NaCl solutions was studied using a wetted wall flow tube equipped with a quadrupole mass spectrometer. The measured uptake coefficient, γexpt, varied between approximately 1 × 10-5 and 1 × 10-4, depending on the aqueous salt concentration. Parameters governing the reactive uptake on NaBr solutions were determined interdependently as H 2 D 1 = (0.101 ± 0.015) M cm2 atm-2 s-2. The accommodation coefficient, α, for ClNO2 on aqueous solutions at 275 K was found to be (9 ± 4) × 10-3. The major gas-phase products of the uptake and reaction of ClNO2 and Br- were found to be Br2 and BrNO2. BrNO2 is formed initially and is converted to Br2 in a secondary reaction with Br- in the aqueous phase. BrCl is a minor product. The presence of 1M Cl- had no effect on either the kinetics of uptake or the products formed. By exchanging the halide solutions for 0.1 M OH-, the uptake rate could be increased so that the diffusion limit was reached in the reactor. Variation of the pressure yielded the diffusion coefficients of ClNO2 in He and N2 as 275 ± 26 and 75 ± 6 Torr cm2 s-1, respectively. The implications of these results for the halogen chemistry of the marine boundary layer are discussed.

A special experimental setup was used to study the equilibrium gas composition after interaction of propene with pure thin polycrystalline nickel films and nickel films precovered with hydrogen under ultrahigh vacuum conditions. Isothermal reaction mass spectrometry allows the analysis of the gas phase composition under equilibrium conditions. The analyzed gas phase consists of desorbed reaction products formed in the adsorbate phase after adsorption of propene on nickel films at 273 K. This technique was combined with thermal desorption spectroscopy and measurements of adsorption-induced changes in the electrical resistance of the polycrystalline films. After interaction with pure nickel films, in addition to propene, hydrogen, methane, propane, and butane could be detected as reaction products. The interaction of propene with nickel films precovered with hydrogen leads to a higher yield of butane and additionally to the formation of pentane. Thermal desorption experiments carried out after adsorption of propene at 77 K show only desorption of hydrogen, when the propene coverage was small. At higher coverages also propene desorbed.