Full-dimensional close-coupling study of rovibrationally inelastic scattering of SiO-H$_2$

Molecular collisional excitation rate coecients are required to interpret spectra of molecular gas not in local thermodynamic equilibrium. Silicon monoxide (SiO) has been detected in a variety of astronomical sources and is of astrophysical importance. Its rovibrational level populations are perturbed by collisions with He, H and H$_2$. The corresponding collisional rate coefficients and their temperature dependence are largely unknown. Theoretical scattering calculations are the primary source of such rate coefficients. In this work a full-dimensional (6D) potential energy surface (PES) of SiO-H$_2$ was calculated using the high-level CCSD(T)-F12B method and fitted using an invariant polynomial approach in 6D. We performed the first full dimensional quantum close-coupling scattering calculations for SiO in collision with H$_2$ on the 6D PES. Pure state-to-state rotational excitation transitions from SiO($v_1=0$, $j_1$=0-10) are computed. For rovibrational transitions, state-to-state and total quenching cross sections and corresponding rate coefficients from several low-lying rotational levels in the first excited vibrational level of SiO are calculated for both para-H$_2$ and ortho-H$_2$ collisions.