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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 10 | Copyright
Atmos. Meas. Tech., 11, 5827-5836, 2018
https://doi.org/10.5194/amt-11-5827-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 23 Oct 2018

Research article | 23 Oct 2018

New and improved infrared absorption cross sections for trichlorofluoromethane (CFC-11)

Jeremy J. Harrison Jeremy J. Harrison
  • 1Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK
  • 2National Centre for Earth Observation, University of Leicester, Leicester LE1 7RH, UK
  • 3Leicester Institute for Space and Earth Observation, University of Leicester, Leicester LE1 7RH, UK

Abstract. Trichlorofluoromethane (CFC-11), a widely used refrigerant throughout much of the twentieth century and a very potent (stratospheric) ozone-depleting substance (ODS), is now banned under the Montreal Protocol. With a long atmospheric lifetime, it will only slowly degrade in the atmosphere, so monitoring its vertical concentration profile using infrared-sounding instruments, and thereby validating stratospheric loss rates in atmospheric models, is of great importance; this in turn requires high-quality laboratory spectroscopic data.

This work describes new high-resolution infrared absorption cross sections of trichlorofluoromethane/dry synthetic air over the spectral range 710–1290cm−1, determined from spectra recorded using a high-resolution Fourier transform spectrometer (Bruker IFS 125HR) and a 26cm pathlength cell. Spectra were recorded at resolutions between 0.01 and 0.03cm−1 (calculated as 0.9/MOPD; MOPD: maximum optical path difference) over a range of temperatures and pressures (7.5–760Torr and 192–293K) appropriate for atmospheric conditions. This new cross-section dataset improves upon the one currently available in the HITRAN (HIgh-resolution TRANsmission) and GEISA (Gestion et Étude des Informations Spectroscopiques Atmosphériques) databases through an extension to the range of pressures and temperatures, improved signal-to-noise and wavenumber calibrations, the lack of channel fringing, the better consistency in integrated band intensities, and additionally the coverage of the weak combination band ν2 + ν5.

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Short summary
CFC-11 is a stratospheric-ozone-depleting molecule which is banned under the Montreal Protocol but still present in the atmosphere due to its long lifetime. Using infrared limb sounders on satellite platforms to monitor its concentration crucially requires accurate laboratory spectroscopic data. This paper describes a new high-resolution infrared absorption cross-section dataset for remote-sensing purposes; this improves upon the one currently available in the HITRAN and GEISA databases.
CFC-11 is a stratospheric-ozone-depleting molecule which is banned under the Montreal Protocol...
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