Empirical line parameters of methane in the 1.63-1.48 µm transparency window by high sensitivity Cavity Ring Down Spectroscopy

Alain Campargue (1, 2) , Le Wang (1) , A.W. Liu (1, 3) , Shui-Ming Hu (4) , Samir Kassi (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
4 Open Laboratory of Bond Selective Chemistry

We have completed the spectral coverage of the 1.58 m transparency window of methane by high sensitivity Cavity Ring Down Spectroscopy at room temperature. The achieved sensitivity (min~310-10 cm-1) allowed measuring line intensities as weak as 310-29 cm/molecule i.e. three orders of magnitude smaller than the intensity cut off of the HITRAN line list of methane. The complete list contains a total of 16223 transitions between 6165 and 6750 cm-1. Their intensity values vary over six orders of magnitude from 1.6×10-29 to 2.5×10- 23 cm/molecule. By comparison with a spectrum of CH3D recorded separately by Fourier Transform Spectroscopy, transitions due to CH3D in “natural” abundance in our methane sample were identified. The relative contribution of the CH3D isotopologue estimated by simulation of the CH3D and methane spectra at low resolution has showed that the CH3D absorption may contribute to the absorption in the region by up to 30%.

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

Alain Campargue, Le Wang, A.W. Liu, Shui-Ming Hu, Samir Kassi. Empirical line parameters of methane in the 1.63-1.48 µm transparency window by high sensitivity Cavity Ring Down Spectroscopy. Chemical Physics, 2010, 373, pp.203-210. ⟨10.1016/j.chemphys.2010.05.011⟩. ⟨hal-00563211⟩