Theoretical Study of the NaO + HCl Reaction: A Potential Formation Route of NaCl in the Interstellar Medium

A preliminary theoretical characterization of the reaction NaO + HCl in the gas phase and in the presence of a cluster of seventeen water molecules has been carried out. The purpose of this explorative study is to investigate the NaCl + OH reaction for the formation of interstellar NaCl, both in the gas phase and on the surface of amorphous ice of interstellar grains. The reaction was seen to occur without entrance barriers to form an adduct that easily evolves into the NaCl + OH products both in the gas phase and in the presence of the cluster of water molecules. In the case of the cluster reaction, we have simulated an Eley-Rideal mechanism in which HCl approaches, from the gas phase, the NaO radical bound to the 17-water-molecules cluster. Both the gas and ice reactions are strongly exothermic and feasible from a thermodynamic standpoint. Furthermore, being barrierless, they are also expected to be fast under the typical conditions of the interstellar medium. Therefore, this process can be added to the list of reactions to be considered as possible formation routes of the diatomic NaCl molecule in the interstellar medium. More work is needed to better describe this system and other similar reactions, such as those leading to KCl, which is also observed in the interstellar medium.