A Comprehensive Data Set of Rotational (De-)excitation Rate Coefficients for SiN in Collisions with He

Abstract We present a complete data set of state-to-state rotational (de-)excitation rate coefficients for the SiN radical in collisions with helium atoms. The data set is derived from high-level ab initio electronic structure calculations at the RCCSD(T)/CBS level with full counterpoise correction, followed by quantum closecoupling scattering calculations that explicitly incorporate the spin-rotation fine structure of the SiN ground electronic state ( 2 Σ + ). The analytical potential energy surface is fitted to the discrete ab initio potential points. Scattering calculations over a collision energy range of 0.1–2000 cm -1 reveal dense sharp resonances below ~30 cm -1 and a strong propensity for Δ n = Δ j transitions. Excitation rate coefficients are provided for temperatures 5–300 K, covering Δ n = Δ j = 1–5 among all fine-structure levels with n < 10. These data fill a critical gap in the collisional data inventory for SiN and provide essential input for non-LTE radiative transfer modeling of SiN-bearing circumstellar and interstellar environments. The dataset that supported the findings of this study is available in Science Data Bank at https://doi.org/10.57760/sciencedb.010ci