Ro-vibrational quenching of molecules of astrophysical, atmospheric and planetary interest.

The advances made in the field of instruments dedicated to astronomy during the last decades and those forthcoming lead to the discovery of an ever growing number of molecules and molecular transitions, the observed spectra becoming more and more precise. To obtain a proper interpretation of this wealth of data and derive physical structure and chemical abundances of the observed media, fundamental data is required to describe the ongoing processes, down to the
microscopic scale. In particular, the inelastic collisions between molecules play an important role in the populating of the rovibrational quantum levels which are observed. In fact, the probability for a molecule to transit from one state to another via molecular collisions at a given temperature is related to the collisional rates. The range of physical conditions reigning in astrophysics requires the knowledge of collisional rates between 5 and a few thousand Kelvin.
As experiments generally do not cover such a wide range, the knowledge of rates heavily relies on theoretical calculations. The computation of  rate coefficients goes though three steps : 1. potential energy surface (ab initio calculation), 2. an analytic numeric fit of this surface and 3. collision calculation giving a precise description of the cross sections and their resonances. Exact quantum calculations will be performed at low temperatures. At higher temperatures, we will resort to approximations such as Monte Carlo quasi-classical approaches.