Dual frequency comb absorption spectroscopy of CH4 up to 1000 Kelvin from 6770 to 7570 cm-1

The high resolution absorption spectrum of methane in the 10 800–14 000 cm−1 region: literature review, new results and perspectives

“…95,96 Optical frequency comb Fourier transform spectroscopy has been applied to the high accuracy absorption measurements of CH 4 transitions in the 1250–1380 cm −1 interval 97 while dual-comb spectroscopy was used in the region of the ν 3 band near 3.4 μm, 98 of the 2 v 3 band near 1.6 μm 99 and in the icosad region (6770–7570 cm −1 ) at high temperature. 100 In our region of interest where the methane absorption is weak, cavity-enhanced absorption is suitable to achieve a sufficient sensitivity. Several high sensitivity cavity-enhanced measurements have been reported by dual-comb spectroscopy mostly in the telecom region ( e.g.…”

“…At high energies, in absence of line lists of methane transitions with known temperature dependence of their intensities, astronomers have adopted a pragmatic approach and use an empirical modelling of low resolution methane spectra. 33,89,90 Karkoschka and Tomasko (KT hereafter) have combined datasets from eight laboratory measurements recorded in a large variety of temperature conditions and measurements from space (Titan's atmosphere spectrum by the Huygens probe, Jupiter spectrum by the Hubble Space Telescope) to provide reliable methane absorption coefficients in the wide 1800-25 000 cm À1 range at three temperatures (100,198 and 296 K). 33 Bowles et al derived methane absorption coefficients and the modelling of their T dependence in the 9000-14 000 cm À1 range on the basis of a series of FTS spectra measured at the Rutherford Appleton Laboratory (UK) over a wide range of pressures (38 mbar to 5 bar), temperatures (100-298 K) and path lengths (14.4-19.3 m).…”