Comprehensive Ab Initio~Calculations of CO2-H2 and CO2-He Collisional Properties

We present comprehensive ab initio calculations of CO ₂-H ₂ and CO ₂-He collisional properties from first principles, employing CCSD (T), potential calculations together with close-coupling dynamical scattering in the ~framework. We derive (in) elastic cross sections, rate coefficients, and pressure-broadening parameters -- incl. , their rotational dependence up to |m|=50, and temperature dependence over the range of 100-800 K. We provide Padé fits for the broadening coefficients as a function of rotational quantum number, enabling extrapolation of the results and integration into spectroscopic databases, including HITRAN and HITEMP. The computed potentials for both CO ₂-H ₂ and CO ₂-He have a sub-percent precision, and the dynamics-solving code YUMI ultimately yields the collisional parameters. Among these, the scaled pressure broadening experimental values meet the 10\% precision requirement for exoplanetary sciences with JWST. This contrasts with the parameters available before the present calculations, which at higher temperatures (T>400 K) deviate as much as 5 from the desired precision requirement. All derivations and collisional properties are provided with this manuscript, establishing the first of such a comprehensive ab initio foundation for collisional systems with a target molecule having more than two atoms.