Reaction between atomic N(4S) and molecular CO at very low temperature: possible formation of HNCO in the Oort cloud

International audienceBeyond the Kuiper belt, the Oort cloud is characterized by particularly cold temperatures and the absence of energetic particles. Specific chemical processes involving cold radicals may occur in this reservoir of comets. A microwave-driven atomic source can be used to generate cold atomic nitrogen (N (4S)) for reactivity study of ices relevant to the Oort cloud. Without any additional source of energy, atomic nitrogen does not react with CO molecules to form NCO. This is consistent with a previous theoretical investigation carried out by Yazidi et al., who have shown that the potential energy surface for the CO (X1Σ+) + N (4S) system is purely dissociative. On the other hand, a very small amount of water is sufficient to induce a reaction between these two species. This three-body reaction leads to the formation of the HNCO monomer, the (HNCO)(H2O) complex, and the hydroxyl radical. Such reactions, leading to prebiotic molecules, may take place in the Oort cloud and in the Kuiper belt, from which most of the comets come