Fully quantum calculations of O 2 -N 2 scattering using a new potential energy surface: Collisional perturbations of the oxygen 118 GHz fine structure line.

A proper description of the collisional perturbation of the shapes of molecular resonances is important for remote spectroscopic studies of the terrestrial atmosphere. Of particular relevance are the collisions between the O ₂ and N ₂ molecules-the two most abundant atmospheric species. In this work, we report a new highly accurate O ₂ (X ³ Σ _g ^- )-N ₂ (X ¹ Σ _g ⁺ ) potential energy surface and use it for performing the first quantum scattering calculations addressing line shapes for this system. We use it to model the shape of the 118 GHz fine structure line in O ₂ perturbed by collisions with N ₂ molecules, a benchmark system for testing our methodology in the case of an active molecule in a spin triplet state. The calculated collisional broadening of the line agrees well with the available experimental data over a wide temperature range relevant for the terrestrial atmosphere. This work constitutes a step toward populating the spectroscopic databases with ab initio line shape parameters for atmospherically relevant systems.