Forming NCO(–) in Dense Molecular Clouds: Possible Gas-Phase Chemical Paths From Quantum Calculations

[Image: see text] The existence of NCO(–) anions in the interstellar medium (ISM) has been suggested and searched for over the years but without any formal definitive sighting of that molecule. We discuss in this work the possible formation of either NCO(–) directly or of NCO neutral as a precursor to NCO(–) formation by electron attachment. We follow simple, gas-phase chemical reactions for which the general features are obtained from accurate quantum calculations. The results are shedding some additional light on the likely presence of this anion in the ISM environment, drawing further information from the specific features of the considered reactions on the additional chemical options that exist for its formation.