Sodium isocyanide–Helium potential energy surface and astrophysical applications

Abstract

In this work, we generated the two-dimensional potential energy surface (2D-PES) of the l-NaNC–He van der Waals interacting system. The electronic computations are done at the CCSD(T)-F12/aug-cc-pVTZ level. This 2D-PES exhibits a unique shallow minimum for helium approaching l-NaNC from the Na atom side. Afterward, we derived an analytical form for this ab initio 2D-PES, which is incorporated into quantum scattering code to compute the rotational (de-)excitation cross sections (rate coefficients) of l-NaNC by collision with He atom for total energies up to 2000 cm−1 (from 5 to 300 K). The propensity rules that favor Δj = − 1 transitions are less pronounced than in the case of t-NaCN isomer. Our data may be used for the determination of the abundances, in astrophysical media, of the candidate isomer l-NaNC with respect to those of the already detected t-NaCN isomer. We also performed comparison with the astrophysical relevant Al- and Mg-bearing (iso)cyanide systems interacting with He.