New potential energy surface and rotational deexcitation cross-sections of CNNC by para-H2 (jp = 0)

Abstract

The objective of this study is to enhance our understanding of the existence of molecules in interstellar space by determining the collisional rate coefficients with the most prevalent species. The study examines the impact of para-H₂ collisions, specifically when it is in its ground vibrational state with a nuclear spin of para-H₂, i.e., j_p = 0, on causing the rotational deexcitation of the diisocyanogen (CNNC) molecule. These scattering data are obtained as a result of spherically averaging a four-dimensional potential energy surface (4DPES) over the H₂ orientations. Using the CCSD(T)-F12a approach and aug-cc-pVTZ basis sets, the ab initio 4DPES for the CNNC–H₂ van der Waals system is calculated. The CNNC–para-H₂ 4DPES attains a global minimum of 221.38 cm⁻¹ at the CNNC and H₂ center of mass distance (R) of 3.1 Å. The method of close coupling calculations is employed for the purpose of calculating the cross-sectional data of CNNC with para-H₂ (j_p = 0), for total energies up to 1000 cm⁻¹. Rate coefficients are computed over the temperature range of 1 K to 100 K. Propensity suggests that even Δj transitions are strongly preferred. The rate coefficients for CNNC–H₂ are determined to be 0.90–2.95 times those of CNNC–He, which implies it is not reliable to estimate the H₂ rate coefficients by multiplying the rate coefficients for CNNC–He collision with a scaling factor of 1.38.