Abstract
The B̃-X̃ laser-induced fluorescence (LIF) and dispersed fluorescence (DF) spectra of the atmospherically important β-monofluoro ethoxy (MFEO), β,β-difluoro ethoxy (DFEO), and β,β,β-trifluoro ethoxy (TFEO) radicals were recorded with vibronic resolution under jet-cooled conditions. To simulate the spectra, Franck-Condon factors were obtained from quantum chemical computations carried out at the CAM-B3LYP/6-311++G(d,p) level of theory. The simulations reproduce well both the LIF and DF spectra. Both conformers (G and T) of MFEO and one (G) of the two conformers of DFEO contribute to the LIF spectrum. A comparison between the experimental and calculated spectra confirms the expected long-range field effects of the CHxF3-x group on electronic transition energies and bond strengths, especially in the excited electronic (B̃) state. Although TFEO has only one conformer, its LIF spectrum is highly congested, which is attributed to the interaction between CO stretch and the -CF3 internal rotation.
Highlights
Hydrofluorocarbons (HFCs) are commonly used as refrigerants, solvents, and propellants, and for etching in the semiconductor industry
The compounds of monofluoroethane (R161), 1,1-difluoroethane (R152a), and 1,1,1-trifluoroethane (R143a) have zero ozone depletion potential (ODP), while their global warming potentials (GWPs, as compared to CO2) are 12, 124, and 4470.1 In addition, each of these compounds is relatively stable in the atmosphere, especially 1,1,1-trifluoroethane, which has an atmospheric lifetime of 40−52 years.[2,3]
All stable conformers except the T conformer of difluoro ethoxy (DFEO) are identified by simulating the spectra
Summary
Hydrofluorocarbons (HFCs) are commonly used as refrigerants, solvents, and propellants, and for etching in the semiconductor industry Their industrial production greatly increased in the late 1980s, because the Montreal Protocol has phased out the production of chlorofluorocarbons (CFCs) that significantly contributed to the depletion of Earth’s ozone layer. The compounds of monofluoroethane (R161), 1,1-difluoroethane (R152a), and 1,1,1-trifluoroethane (R143a) have zero ODP, while their global warming potentials (GWPs, as compared to CO2) are 12, 124, and 4470.1 In addition, each of these compounds is relatively stable in the atmosphere, especially 1,1,1-trifluoroethane, which has an atmospheric lifetime of 40−52 years.[2,3] Realizing this problem, more than 150 nations have agreed in to cut back their HFC use from 2019. Even if their production would drastically decrease in the few years, due to their long atmospheric lifetime, HFC pollutants will be present in the atmosphere for decades
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