Measuring OH and HO₂ in the troposphere by laser-induced fluorescence at low pressure

The hydroxyl radical OH oxidizes many trace gases in the atmosphere. It initiates and then participates in chemical reactions that lead to such phenomena as photochemical smog, acid rain, and stratospheric ozone depletion. Because OH is so reactive, its volume mixing ratio is less than one part per trillion volume (pptv) throughout the troposphere. Its close chemical cousin, the hydroperoxyl radical HO₂, participates in many reactions as well. The authors have developed an instrument capable of measuring OH and HO₂ by laser- induced fluorescence in a detection chamber at lower pressure. This instrument is now being adapted to aircaraft use for measurements throughout the troposphere. -from Authors