Air broadening coefficients for the ν3 band of hydroperoxyl radicals

•Mid-infrared absorption spectra of HO2 measured in the presence of N2 or O2.•The air broadening coefficients of HO2 were determined in the ν3 band.•The dependence of air broadening on rotational states is discussed.

Using mid-infrared laser absorption spectroscopy, we investigated the room-temperature pressure broadening coefficients for hydroperoxyl radicals (HO2) in nitrogen and oxygen over the 1060.0-1065.5 cm−1 range of the ν3 band. The HO2 radicals were produced by flash photolysis of a chlorine/1,4-cyclohexadiene/oxygen mixture. The 20 measured absorption profiles were analyzed with Voigt functions. Air broadening coefficients were estimated from the nitrogen- and oxygen-broadening results and compared with previous results. We discuss the dependence of air broadening on rotational states.