Atmospheric infrared emission of ClONO₂ observed by a balloon‐borne Fourier spectrometer

ClONO 2 was observed in high‐resolution infrared emission spectra obtained on November 6, 1984, by a balloon‐borne Fourier spectrometer. The observations took place near 0300 LT at a latitude of 35°N. Spectral simulations are used to determine the mixing ratios of ClONO 2 . This analysis incorporates line by line calculations and new ClONO 2 cross sections measured in the laboratory at 223 K. The inferred mixing ratios of ClONO 2 are 1.3±0.45 ppb and 0.98±0.35 ppb at 14 and 34 mbar. One‐dimensional photochemical model predictions are compared to the observations. The ClONO 2 mixing ratio at 34 mbar appears to be larger than theory, while there is agreement at 14 mbar.