Laser absorption spectroscopy of methane at 1000 K near 1.7 µm: A validation test of the spectroscopic databases

Abstract A tubular furnace is combined with a diode laser spectrometer to record the high temperature near infrared absorption spectrum of methane at a pressure of 80 Torr. The investigated spectral range covers the 5693–6257 cm −1 (1.75–1.60 µm) range of the tetradecad dominated by the 2ν 3 band near 6000 cm −1 . Various determinations (thermocouples, Doppler line broadening, rotational temperature) provide a value of about 964 K for the gas temperature. Lines with intensity larger than 5 × 10 −24  cm/molecule at 1000 K are detected. As a result of the high temperature, high- J rovibrational transitions up to J  ≈ 20 and hot bands are identified in the spectrum. The recorded spectra provide tests of various methane line lists recently released in the literature: HITRAN2016, experimental list derived from emission spectra, the MeCaSDa empirical line list and the TheoReTs and ExoMol theoretical line lists. The agreement with the TheoReTs line list is found to be very good in the studied region.