Abstract
Fluorocarbon-12 (CCl<sub>2</sub>F<sub>2</sub>) has been detected in the atmosphere by observation of infrared solar spectra in two spectral regions of the 8 to 12 μm atmospheric transmission window. The solar spectra were compared with laboratory spectra of CCl<sub>2</sub>F<sub>2</sub> and also with computer synthesized spectra which were generated from the most recent Air Force Cambridge Research Laboratories line parameters listing. Water vapor lines interfere with strong Q-branch absorption features of CCl<sub>2</sub>F<sub>2</sub> in the spectral region near 923 cm<sup>−1</sup>. The region near 1161 cm<sup>−1</sup> is free from water vapor absorption and has the strongest Q-branch feature of CCl<sub>2</sub>F<sub>2</sub>. Many laboratory spectra of CCl<sub>2</sub>F<sub>2</sub> were studied and this absorption feature was found to be independent of N<sub>2</sub> broadening pressure. No change in the half-width was found as the N<sub>2</sub> pressure was varied from 0 to 700 Torr. Furthermore, assuming a Lorentz line shape for this CCl<sub>2</sub>F<sub>2</sub> absorption feature, an intensity of 3.8 × 10<sup>−18</sup> cm<sup>.</sup> molecule<sup>−1</sup> and a half-width of 0.026 cm<sup>−1</sup> were found. Using these parameters, synthetic solar spectra were computed which included the CCl<sub>2</sub>F<sub>2</sub> absorption feature. Results of this computer generation of solar spectra indicate a ground level concentration of 110 parts per trillion of CCl<sub>2</sub>F<sub>2</sub> in our solar spectra.
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