On the Formation and Detectability of H2CNCN and Its Progenitors

Abstract

New highly exothermic formation pathways incorporating both thermodynamic and kinetic control for the newly astronomically detected H _2 CNCN molecule are paired with extremely accurate quantum chemical rovibrational spectroscopic computations. The reactions between astronomically known CH _2 CN/CH _2 CCH + HNCN follow effectively identical pathways and proceed through stable intermediates and over deeply submerged transition states to form H _2 CNCN and HCN/HCCH coproducts. Similarly, the reaction between CH _2 CN and NCN ^− can also form H _2 CNCN, although this pathway first requires the initial formation of NCN ^− , which is currently undetected in space, via HNCN + CN ^− . This two-step mechanism uses the highly abundant CN ^− as the catalyst. Incredibly accurate quantum chemical spectroscopic data are reported for all reactants and products of these reactions, with errors between experimental values and the computations herein on the order of 0.1% or less. Anharmonic vibrational frequencies and intensities are also reported in order to guide experimental and observational searches for these molecules that have mostly been detected in the radio but may now be detectable via JWST.

Keywords

• Infrared spectroscopy
• Rotational spectroscopy
• Molecular reactions
• Ion-neutral reactions
• Interstellar medium