Ab initio investigation of the CO–N₂ quantum scattering:The collisional perturbation of the pure rotational R(0) line in CO

Collisions with the nitrogen molecule perturb the absorption lines of less abundant molecules in the Earth’s atmosphere, leading to the pressure broadening of the spectra which constitutes the primary broadening mechanism in the troposphere. Accurate values of pressure broadening and shift coefficients are essential for reducing atmospheric-spectra fit residuals, which might affect values of the quantities retrieved from the fit. This is especially important in terms of remote sensing of gaseous pollutants, such as the CO molecule. Accurate pressure broadening coefficients of the N₂-perturbed CO lines are also needed in the analysis of the nitrogen-dominated atmospheres of Titan, Triton or Pluto.

We report fully quantum calculations of the collisional perturbation of the N₂-perturbed pure rotational R(0) line in CO. The results agree well with the available experimental data. This work constitutes a significant step toward populating the spectroscopic databases with ab initio collisional line-shape parameters for atmosphere-relevant systems. The calculations were performed using three different recently reported potential energy surfaces (PESs). We conclude that all three PESs lead to practically the same values of the pressure broadening coefficients.