Kinetics of the reactions of BrHg radical with NO₂ and O₃

Laser photolysis-laser induced fluorescence (LP-LIF) spectroscopy was used for the first experimental kinetic study of the atmospherically important reactions of BrHg + Y, where Y is the abundant free radicals in the atmosphere, such as NO₂ and O₃. We measured the rate constants of the reactions of BrHg + Y versus temperature (313 – 373 K) and pressure (80 – 700 Torr), and derived the parameters of the Troe expression to assist the modeling of atmospheric mercury redox. The experimental result of the reaction of BrHg + NO₂ was compared with the previous computational study, which confirmed that the major competing channel should be assigned to the predicted mercury reduction reaction. The addition rate constants in the high-pressure limit of the two studies are consistent, but the discrepancies suggest that the computation has overestimated the efficiency of collisional energy transfer, which leads to an overestimation of the rate constants in the low-pressure limit. The result of the reaction of BrHg + O₃ suggests a significant side reaction – BrHgO + O₃ → BrHg + 2O₂ – that hasn’t been studied before.