The CW-Cavity Ring Down Spectrum of CH4 has been recorded in the 1.55 µm transparency window with a very high sensitivity

A.W. Liu (1) , Samir Kassi (1) , Alain Campargue (1)

1 LSP - Laboratoire de Spectrométrie Physique

The high resolution absorption spectrum of methane has been recorded at room temperature by high sensitivity CW-Cavity Ring Down Spectroscopy between 1.50 and 1.60 m (6250-6680 cm-1). This spectral region has a low opacity and is then of particular interest for the spectral analysis of the outer planets and Titan. The recordings were performed with a sensitivity corresponding to a noise equivalent absorption of min~510-10 cm-1 and allowed for the detection of lines with an intensity smaller than 10-28 cm/molecule far beyond the weakest lines provided by the HITRAN database. The spectrum exhibits a highly complex and congested structure with a kind of “fractal” character and a density of transitions of a few tens per cm-1. The impact of the weak newly observed transitions on the total absorption in the region is discussed.

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

A.W. Liu, Samir Kassi, Alain Campargue. The CW-Cavity Ring Down Spectrum of CH4 has been recorded in the 1.55 µm transparency window with a very high sensitivity. Chemical Physics Letters, 2007, 447, pp.16. ⟨10.1016/j.cplett.2007.08.092⟩. ⟨hal-00563181⟩