Halogen Oxides in the Troposphere (ClO/BrO)

Measurement Description: Halogen oxides (ClO and BrO in this configuration) are rapidly converted to halogen atoms by addition of nitric oxide. The atoms are then detected sensitively and selectively by resonance fluorescence in the vacuum ultraviolet (Cl at 118.9 nm and Br at 131.7 nm). For measurements of BrO in the troposphere the pressure of the air sample must be reduced to less than 100 hPa, else oxygen in the flow absorbs all the radiation at 131.7 nm. On the DC-8 this pressure reduction will be accomplished by incorporating our detection system into the ATHOS (Brune and colleagues, Penn State) sampling system, which uses Laser-Induced Fluorescence at low pressure to detect OH and HO2.