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Combining experimental spectra and density functional theory for improved global warming potential calculations


Temperature-dependent absorption cross sections of several fluorinated molecules considered to be greenhouse gases due to being radiatively active in the mid-infrared are presented. Experimental absorption cross-sections were derived from Fourier transform infrared spectra recorded from 530 to 3400 cm^-1 with a resolution of 0.1 cm^-1. These results were compared to theoretical density functional theory (DFT) calculations and previously published experimental measurements made at room temperature. Theoretical DFT calculations were performed using the B3LYP method and a minimum basis set of 6-311++G(d,p). The DFT spectra can be calibrated to match the experimental spectra, increasing its accuracy. Using the adjusted DFT-calculated spectra, the wavenumber range is extended beyond the experimental range when calculating radiative efficiencies and global warming potentials. When the spectral range is extended using the DFT spectra, the radiative efficiency and global warming potential increase, suggesting that the current values are underestimating the climate impacts of these species.