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, H-2, and e). The main goals of this paper are to study the collision of the NO+ molecule with para-H-2 (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 II/ orientations was then fitted using a reproducing kernel Hilbert space procedure. The state-to-state cross-sections of NO++para-H-2 (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.