Heterogeneous Interaction and Reaction of HOBr on Ice Films

The uptake coefficient γ of HOBr on the ice surface from 190 to 239 K has been investigated in a flow reactor interfaced with a differentially pumped quadrupole mass spectrometer. γ of HOBr on ice is in the range 0.11−7 × 10 -3 at 190−218 K and is in the range 2 × 10 -3 to 6 × 10 -4 at 223−239 K. The desorption temperature T d of HOBr on the ice film was determined. T d increases with the HOBr exposure. The Monte Carlo simulation was used to shed light on the nature of the desorption and gas−surface interactions. This study extends our investigations to the reaction probability of the HOBr + HCl reaction. The reaction probability ranges from 0.05 to 0.23 at 190 K and 0.004 to 0.19 at 222 K as a function of P HCl, which varies from 1.3 × 10 -7 to 8.8 × 10 -6 Torr and 4.2 × 10 -7 to 1.5 × 10 -5 Torr, respectively. Kinetic analysis indicates that the heterogeneous reaction of HOBr + HCl follows the Langmuir−Hinshelwood type.