Relaxation of NO⁺ by collision with para-H₂ (j = 0)

The first tentative detection of the nitrosylium ion (NO⁺) in the interstellar medium (ISM) was reported just a few years ago. The application of non-local thermal equilibrium models requires the knowledge of the collisional rate coefficients with the most common colliders in the ISM (e.g. He, H, H₂, and e). The main goals of this paper are to study the collision of the NO⁺ molecule with para-H₂ (j = 0) and report the rate coefficients for the lower rotational states of NO⁺. A large set of ab initio energies was computed at the CCSD(T)/aug-cc-pV5Z level of theory. A new potential energy surface averaged over the H₂ orientations was then fitted using a reproducing kernel Hilbert space procedure. The state-to-state cross-sections of NO⁺+para-H₂ (j = 0) for the first 18 rotational levels were computed using the close-coupling method. The rotational rate coefficients of this system were compared with those for NO⁺+He, and a different propensity rule was found. Furthermore, the hyperfine rate coefficients were also calculated using the infinite-order-sudden scaling procedure.