Detection of atmospheric 15NO2 in the ν3 spectral region (6.3 μm)

A reinvestigation of the ν3 band of 15NO2 has been performed using experimental data acquired in 2000 [Orphal J, Perrin A, Flaud JM, Smirnov M, Himmelmann, Voigt S, Burrows JP. J Mol Spec 2000;204:72-9]. The linelist generated in this way during this study was used to detect this isotopologue in the atmosphere for the first time, using balloon-borne solar occultation spectra measured by the JPL MkIV Fourier transform spectrometer. It is shown that over the 15-35 km altitude range where 15NO2 can be detected, the retrieved 15/14 NO2 ratio is within 5% of the expected value (0.00364), implying that the absolute line intensities in the new linelist are accurate. Over the same altitude range the RMS spectral fitting residuals reduce significantly as a result of including the new 15NO2 linelist, improving the accuracy of retrievals of all gases that absorb in the 1550-1650 cm−1 region (e.g., 14NO2, H2O, HDO, O2).