Quantum Scattering Study of NCCNH⁺-H₂ Collision Under Interstellar Conditions

The rotational dynamics of protonated cyanogen (NCCNH⁺) is studied for collision with both para (p-) and ortho (o-) hydrogen (H₂) in the temperature range $1-100$ K. Such cold collisions with H₂ are essential to get state-to-state rate coefficients for rotational transitions of newly detected NCCNH⁺. First, the ab initio 4D potential energy surface (PES) for NCCNH⁺-H₂ collision is generated at CCSD(T)-F12b level of theory using augmented triple zeta basis, considering rigid rotor approximation. The 4D PES is further fitted into a neural network (NN) model to augment the PES by $\sim 130$ folds. The PES is then expanded using bispherical harmonics functions to get radial terms, which are expressed as analytic functions. The cross-sections and rate coefficients for NCCNH⁺ are calculated using the exact close-coupling method for rotational states up to $j=16$ , considering both p- and o-H₂ collisions. The rates show similar behavior to the earlier studied NCCN-H₂ collision, with the latter having larger rate coefficients.