Abstract
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 710–1290 cm−1, determined from spectra recorded using a high-resolution Fourier transform spectrometer (Bruker IFS 125HR) and a 26 cm pathlength cell. Spectra were recorded at resolutions between 0.01 and 0.03 cm−1 (calculated as 0.9/MOPD; MOPD: maximum optical path difference) over a range of temperatures and pressures (7.5–760 Torr and 192–293 K) 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.
Highlights
Chlorofluorocarbons (CFCs) were first developed in the 1930s as safe, reliable, and non-toxic refrigerants for domestic use
Trichlorofluoromethane, known as CFC-11 or Freon-11, and dichlorodifluoromethane, known as CFC-12 or Freon-12, were the two most widely used CFCs in applications ranging from refrigerators and air conditioners to propellants in spray cans and blowing agents in foam production
Banks are the major source of emissions for many ozone-depleting substances (ODSs), including CFC-11, which has a long atmospheric lifetime of 52 years (Harris et al, 2014)
Summary
Chlorofluorocarbons (CFCs) were first developed in the 1930s as safe, reliable, and non-toxic refrigerants for domestic use. The explosion in their use led to a steady increase in their atmospheric abundances While they are inert in the troposphere, it was this stability which enabled them to reach the stratosphere, where dissociation by ultraviolet radiation released chlorine atoms, which catalyse the destruction of stratospheric ozone (Solomon, 1999). The realisation of this impending environmental disaster prompted international action, and in 1987 the Montreal Protocol was ratified; this led to the phasing out of the worldwide production and use of CFCs. CFCs are still released into the atmosphere from “banks”, such as old refrigerators; these are not regulated by the protocol (Harris et al, 2014). TRANsmission; Gordon et al, 2017) and GEISA (Gestion et Étude des Informations Spectroscopiques Atmosphériques; Jacquinet-Husson et al, 2016) databases
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