Collisional excitation of CO2 by He : New potential energy surface and scattering calculations

International audienceThe correct modeling of the ionization fraction in protoplanetary disks requires the prior estimation of the chemical composition of the matter. Molecular abundances in non-LTE media such as protoplanetary disks are obtained thanks to radiative transfert models that considers excitation of molecules by both collisions and radiations. Since CO2 is known to be an abundant molecule in protoplanetary disks, which are caracterized by temperatures below 200 K, it is then of interest to study its collisional excitations. In this talk, I will present our recent study of the astrophysically relevant CO2-He collisional system which is also a prototypical system for more complex CO2-bearing systems. A new potential energy surface was calculated with a Coupled Cluster method and a complete basis set extrapolation. Its accuracy was tested through the comparison of bound states and pressure broadening coefficients with experimental measurements. Finally, revised collisional data were provided in the 10-300 K temperature range. These new data can lead to a revision of the CO2 abundance and thus, to the physical conditions, such as the ionization fraction, in astrophysical media were CO2 is present