Summary:

The modeling and interpretation of molecular spectra from interstellar environments require the knowledge
of both radiative and collisional processes of energy transfer between chemical species. Accurate
state-to-state rate coefficients of interstellar molecules in collision with the main collisional partners H2,
H and He are then necessary.

Such collisional data can be obtained through quantum time-independant scattering calculations by
resolving the close-coupled equations. This method is nowadays one of the most accurate for describing
collisions at very low temperature. However, species such as radicals possess very complex energetic
structures because of the presence of non zero electronic and even nuclear spins. Also, accurate description
of fine and hyperfine transitions implying two interacting molecules is a true theoretical challenge.
Then, this method is not fully applicable in terms of memory and CPU time.

This thesis work consists in quantifying the collisional excitation of these open-shell molecules in astrophysical
media. The development of methodological and numerical tools are then required to overcome
these problems and to characterize physical and chemical processes as precisely as possible. The provided
collisional data are expected to interpret observations and corroborate experiments performed in
laboratory.

For more information please contact Scribano Y.