Heterogeneous Interaction and Reaction of HOBr on Ice Films

Abstract

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 Td of HOBr on the ice film was determined. Td 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 PHCl, 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.