Quantum dynamics of C7N- and C10H- anions in collision with H2 at interstellar medium conditions

Abstract

We present quantum calculations for two of the longest linear anions, recently detected in the interstellar environments: C7N- and C10H-, in collision with the most abundant neutral partner in the same environment: the H2 molecule. The interaction forces are obtained from accurate ab initio calculations for the two partners as rigid rotors, generating a dense grid of potential energy values in four dimensions. The potential energy surface is, in turn, fitted by using high-level neural network procedures, and multipolar expansion coefficients are obtained to provide input for calculations of the collision-induced rotational energy transfer processes at the temperatures of interstellar environments. Cross sections are used to generate state-to-state inelastic rate coefficients up to 50 K. The results for the cases of ortho- and para-H2 as collision partners are discussed and analyzed.