Experimental low energy values of CH4 transitions near 1.33 µm by absorption spectroscopy at 81 K

Ella Sciamma O'Brian (1) , Samir Kassi (1, 2) , Gao Bo (1, 3) , Alain Campargue (1, 2)

1 LSP - Laboratoire de Spectrométrie Physique
2 LAME-LIPhy - LAsers, Molécules et Environnement
3 Hefei National Laboratory for Physical Sciences at Microscale, Department of Chemical Physics

The high resolution absorption spectrum of methane has been recorded at liquid nitrogen temperature by direct absorption spectroscopy between 1.36 and 1.30 m (7351- 7655 cm-1) using a cryogenic cell and a series of Distributed Feed Back (DFB) diode lasers. The investigated spectral range corresponds to the high energy part of the icosad dominated by the 2+23 band near 7510 cm-1. The positions and strengths at 81 K of 3473 transitions were obtained from the spectrum analysis. The minimum value of the measured line intensities (at 81 K) is on the order of 10-26 cm/molecule i.e. significantly lower than the intensity cut off of the HITRAN database in the region (4×10-25 cm/molecule at 296 K). From the variation of the line strength between 81 K and 296 K, the low energy values of 1273 transitions could be determined. They represent 69 and 81% of the absorbance in the region at 296 and 81 K respectively. The obtained results are discussed in relation with the few rovibrational assignments previously reported in the region.

Domaines: Physique Atomique [physics.atom-ph]; Optique [physics.optics]

Ella Sciamma O'Brian, Samir Kassi, Gao Bo, Alain Campargue. Experimental low energy values of CH4 transitions near 1.33 µm by absorption spectroscopy at 81 K. Journal of Quantitative Spectroscopy and Radiative Transfer, 2009, 110, pp.951-963. ⟨10.1016/j.jqsrt.2009.02.004⟩. ⟨hal-00563209⟩