Rovibrational inelastic scattering in the CO-H$_ 2$ complex

Rovibrational inelastic collisional rate coefficients for the CO-H$_2$ system have significant application in interstellar astronomy. In an attempt to address this need, we present quantum coupled-channel calculations of rovibrational state-to-state and total cross sections and rate coefficients. Full dimensional close-coupling (CC) and coupled-states (CS) approximation scattering calculations were carried out on a full-dimensional (6D) potential energy surface (PES), which was obtained using the high-level CCSD(T)-F12B method and fitted using an invariant polynomial approach in 6D. Pure state-to-state rotational excitations from CO($v_1=0$, $j_1$=0, 1) were benchmarked with crossed molecular beam measurements. For rovibrational transitions, quenching cross sections and rate coefficients were calculated for the vibrational quenching of rovibrationally excited CO and H$_2$. The resulting data are compared with experimental results and previous calculations which used 4D PESs and various decoupling approximations, where available. Work is on-going to extend the computations to high-lying initial rovibrational levels though CC calculations in 6D require enormous computational resources.