Temperature-dependent absorption cross-sections in the thermal infrared bands of SF 5CF 3

Abstract

Absorption cross-sections have been measured at five temperatures between 213 and 323 K in the infrared bands of SF 5CF 3. The spectra were recorded at a resolution of 0.112 cm −1 using a commercial Fourier transform infrared spectrometer and a 20 cm temperature-controlled sample cell. Samples of SF 5CF 3 were pressurized with high-purity nitrogen to a total pressure of 1013.3 hPa (760 Torr) . Six or more spectra with varying SF 5CF 3 column amounts were analyzed at each temperature. The full spectral range of the measurements was 520– 6500 cm −1 , with only weak bands observed beyond 1400 cm −1 . Absorption of thermal radiation in the 8– 12 μm atmospheric window region being important for climate change, we report here the integrated cross-sections of the significant absorption bands in that spectral region. Our results closely match room temperature values reported previously. Only small variation of the integrated absorption cross-sections with temperature was found. Our results confirm the accuracy of the previous measurements, which find SF 5CF 3 important for global climate change on a per molecule basis. Absorption cross-sections derived from a single, near Doppler-limited spectrum recorded at room temperature do not show any rotational fine structure in the 700– 950 cm −1 region.