Measurements of perfluoro-n-heptane and perfluoro-n-octane absorption cross-sections from 300 to 350 K

Abstract

Perfluoroalkanes are fully fluorinated greenhouse gases. These compounds are chemically inert due to their C–F bonds and therefore have atmospheric lifetimes of thousands of years. Although regulated under the Kyoto Protocol, atmospheric concentrations of perfluoroalkanes have continued to increase since 1997. To quantify the climate impact of perfluoro-n-heptane and perfluoro-n-octane, spectral data are required to calculate climate metrics such as the radiative efficiency and global warming potential. Experimental measurements are scarce for these compounds and are only available at 296 and 297 K. In this work, a set of absorption cross-sections is provided in the range 515–1500 cm⁻¹ at 0.1 cm⁻¹ resolution for nine temperatures between 300 and 350 K. There is general agreement between literature values and the absorption cross-sections and climate metrics measured in this work. These quantities do not show significant temperature dependence. The temperature averaged radiative efficiency is 0.50 ± 0.06 and 0.54 ± 0.07 Wm⁻²ppbv⁻¹ for n–C₇F₁₆ and n–C₈F₁₈, respectively. The temperature averaged 100-year global warming potential is 8738 ± 1149 for n–C₇F₁₆ and 8392 ± 1103 for n–C₈F₁₈.