Fine-structure-resolved Rovibrational Excitation of OH due to Collisions with H₂

Recent JWST observations of the fundamental rovibrational band of OH provide motivation for accurate collisional data, particularly for modeling systems outside local thermodynamic equilibrium. These observations highlight the need for reliable state-resolved scattering calculations for open-shell diatom-molecule collisions.

We report quantum scattering results for OH-H₂ collisions based on a newly developed full-dimensional potential energy surface. Rovibrationally inelastic rate coefficients are computed using a five-dimensional coupled-states approximation and validated through comparison with full close-coupling calculations. Fine-structure splitting and Λ-doubling are explicitly accounted for in the dynamics. We believe these are the first calculations for this collision system to consider rovibrational transitions at this level of detail.