Abstract
Abstract. Despite its widespread commercial use throughout the twentieth century, primarily in the refrigeration industry, dichlorodifluoromethane (CFC-12) is now known to have the undesirable effect of depleting stratospheric ozone. As this long-lived molecule slowly degrades in the atmosphere, monitoring its vertical concentration profile using infrared sounders on satellite platforms crucially requires accurate laboratory spectroscopic data. This work describes new high-resolution infrared absorption cross sections of dichlorodifluoromethane over the spectral range 800–1270 cm−1, determined from spectra recorded using a high-resolution Fourier transform spectrometer (Bruker IFS 125HR) and a 26 cm pathlength cell. Spectra of dichlorodifluoromethane/dry synthetic air mixtures 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 (7.5–761 Torr and 190–294 K) appropriate for atmospheric conditions. This new cross-section dataset improves upon the one currently available in the HITRAN and GEISA databases.
Highlights
Modern civilisation owes much to refrigeration, from medical applications such as the preservation of tissues and organs, and the manufacture and transport of drugs, to the air conditioning of vehicles, homes, offices, and factories, and the manufacture, storage, and transport of food
All air-broadened dichlorodifluoromethane IR spectra were recorded at the Molecular Spectroscopy Facility, Rutherford Appleton Laboratory, UK, using a Bruker Optics IFS 125 HR FTS operated by Bruker’s OPUS software
Note that using Pacific Northwest National Laboratory (PNNL) spectra for intensity calibration effectively nullifies the errors in the dichlorodifluoromethane partial pressures and cell pathlength, so these do not have to be included in Eq (3)
Summary
Modern civilisation owes much to refrigeration, from medical applications such as the preservation of tissues and organs, and the manufacture and transport of drugs, to the air conditioning of vehicles, homes, offices, and factories, and the manufacture, storage, and transport of food It was the food industry which provided the driving force for refrigeration technologies in the late nineteenth and early twentieth centuries; storing perishable foodstuffs of animal and plant origin at low temperatures reduces bacterial growth, minimising the chances of contracting food-borne illnesses (Rees, 2013). The uses for CFCs climbed steadily worldwide over the following decades; in addition to refrigerants for refrigerators and air conditioners, they were used, for example, as aerosol propellants, blowing agents, and solvents This steady climb in production was matched by a rise in their atmospheric concentrations.
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