A Combined Crossed Molecular Beam and Theoretical Investigation of the CN(X2Σ+) + HCCCN and CN(X2Σ+) + H2CCHCN Reactions and Astrophysical Implications

CN is one of the most abundant and widespread radicals in the interstellar medium The fast reactions between CN and unsaturated hydrocarbons generate various nitriles including HC₃N and H₂CCHCN, which are alleged to be prebiotic molecules HC₃N is ubiquitous in interstellar environments Similarly, H₂CCHCN has also been detected in numerous objects, such as the dark cloud TMC 1 massive star forming regions Sgr B 2 and Orion KL, the circumstellar envelope of the C rich star IRC 10216 and Titan's atmosphere. Because of the wide distribution of these species, it is interesting to explore if the reactivity of CN with HC₃N and H₂CCHCN can produce more complex nitriles Kinetics studies confirmed that the rate constant for the CN (X²∑⁺) + HC₃N reaction increases rapidly as the temperature decreases from 300 K to 22 K while few studies have focused on the CN(X²∑⁺) + H₂CCHCN reaction Furthermore, there are no experimental data on the reaction products and their branching ratios Given these open questions, it is essential to gain further insights into these elementary reactions, both experimentally and theoretically.