A Scalable Quantum Dynamical Approach for Calculating Collisional Molecular Properties

An unprecedented increment in the information content of exoplanetary datasets has highlighted a key bottleneck in their interpretation: a lack of fidelity of our models. One of such deficiencies is rooted in how well we model light-matter interactions (a.k.a. opacity models) and, thus, translate spectral data into physical inferences. High-fidelity models are necessary for robustly constraining the molecular abundances and reliably detecting life elsewhere. Opacity models are primarily built up and extrapolated from laboratory studies, which are both time and resource-intensive. Here, we present an alternative method for calculating collisional molecular properties from ab initio calculations, thereby paving a path for an efficient, scalable solution for the much-needed model upgrade. We have successfully demonstrated the feasibility of our approach by successfully calculating the collisional properties for CO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>-H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> in approximately 25,000 CPU hours. With an achieved scaling of $\mathcal{O}\left( {{N^2}} \right)$, and ongoing efforts including sparse matrix optimizations, our method is extendable to more complex systems such as H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O-H<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>. This enables systematic and timely expansion of spectroscopic databases required for robust exoplanetary atmospheric retrievals in the JWST era.