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

The CO2 molecule is of great interest for astrophysical studies since it can be found in a large variety of astrophysical media where it interacts with the dominant neutral species, such as He, H-2, or H2O. The CO2-He collisional system was intensively studied over the last two decades. However, collisional data appear to be very sensitive to the potential energy surface (PES) quality. Thus, we provide, in this study, a new PES of the CO2-He van der Waals complex calculated with the coupled-cluster method and a complete basis set extrapolation in order to provide rotational rate coefficients that are as accurate as possible. The PES accuracy was tested through the calculations of bound state transition frequencies and pressure broadening coefficients that were compared to experimental data. An excellent agreement was globally found. Then, revised collisional data were provided for the 10-300 K temperature range. Rate coefficients were compared to previously computed ones and are found to be up to 50% greater than previously provided ones. These differences can induce non-negligible consequences for the modeling of CO2 abundance in astrophysical media. Published under an exclusive license by AIP Publishing.

Automated summary

This study provides a new potential energy surface (PES) of the CO2-He van der Waals complex calculated with the coupled-cluster method and a complete basis set extrapolation, aiming to provide accurate rotational rate coefficients. The accuracy of the PES was tested through calculations of bound state transition frequencies and pressure broadening coefficients, showing excellent agreement with experimental data. Revised collisional data for the 10-300 K temperature range were provided, with rate coefficients found to be up to 50% greater than previously computed ones, potentially impacting the modeling of CO2 abundance in astrophysical media.