Ab initio quantum scattering calculations for modeling collision-perturbed molecular spectra

Accurate description of collisional effects in shapes of optical resonances is crucial for a reliable interpretation of molecular spectra and reduction of systematic errors in atmospheric measurements. We present a theoretical description of the shape of molecular spectra based on quantum scattering calculations performed on ab initio potential energy surfaces. We investigate molecular systems important in the astrophysical context (HD-H₂), relevant to studies of Earth’s atmosphere (CO-N₂, O₂-N₂, CO-O₂, HCl-O₂) and ultra-accurate spectroscopy for fundamental studies (H₂-H₂ and D₂-D₂). We present computational tools developed in our group and we address the challenges in solving coupled-channels equations in diatom-diatom systems. We discuss the application of the results presented here to the construction of a new generation of line-by-line spectroscopic databases populated with collisional line-shape parameters calculated from first principles.