Spectroscopy activities

"Spectroscopy of Molecules of Atmospheric Interest" is a research activity present at LISA since January 2005. Spectroscopy enables one, through the analysis of spectral signatures reflecting the interactions between molecules and radiation, to determine the molecular structures as well as to understand the intramolecular interactions. It is also a means of probing the inter-molecular potential energy surfaces that, via collisions, affect the shape of the absorption spectra.

The spectroscopic researches at LISA encompass such fundamental studies, which can then be used for various applications, environmental, industrial, biological... Optical measurements are indeed among the means, used mostly by the geo and astrophysicists, to remotely obtain information on planetary (including earth) and cometary atmospheres, as well as on the interstellar medium. Indeed, the signatures of various gaseous species in the corresponding recorded spectra provide access to the composition of the investigated medium. With this goal, great efforts are currently being implemented by space agencies (CNES, ESA, NASA,...) to develop observation instruments (spectrometers, ground based or onboard satellites and probes, radio astronomy observatories, etc). The quality of the results deduced from these observations is obviously dependent on the accuracy of spectroscopic parameters used to analyze the measurements. The spectra of small molecules of pre-biotic or biological interest are also studied with the aim to provide structural information, data on photochemical stability and to validate quantum chemistry calculations for larger systems.

The researchers involved in these spectroscopic studies do consider, both experimentally and theoretically, all the aspects, fundamental as well as applied, related to the interpretation of molecular spectra in a wide spectral range (microwave, infrared, UV, VUV).

The main research axes are :

- Axis 1 : Experimental laboratory spectroscopy and instrumental developments in order to measure line parameters (positions, absolute intensities, spectral profiles and cross sections) using Fourier transform spectrometers, tunable laser sources and synchrotron radiation.

- Axis 2 : Theoretical modeling and spectral analyses

- Axis 3 : From laboratory spectroscopy to the study of the universe which implies:


  • Obtaining spectroscopic data for many atmospheric and astrophysical molecules
  • Generating and collecting spectroscopic parameters to complete/improve spectroscopic databases (HITRAN$, GEISA$, MIPAS$, JPL$, CDMS$, SPATALOG$...) widely used by the scientific community
  • Evaluating the consequences of our spectroscopic results for the simulation, treatment and analysis of atmospheric or astrophysical spectra.

- Axis 4 : The study of atmospheres that relies on the developed spectroscopic knowledge, for which we:

  • Perform recordings of spectra of the Earth atmosphere
  • Retrieve vertical profiles of atmospheric species from the inversion of atmospheric spectra. These profiles are used for environmental/chemical composition studies as well as for the test and validation of atmospheric chemistry and transport models
  • Some activities including the expertise, treatment and analysis of spectra recorded by instruments onboard satellites for the observation of the Earth. Such studies are supported by contracts with large French and European agencies (blind/CNRS, ANR, CNES, ESA, CEE…).