Some Properties of H₂CN⁺: a Potentially Important Interstellar Species

Ah initio quantum-mechanical electronic-structure calculations have been performed on the molecular ion H2CN+. Geometries have been predicted for both the acetylene-like ( ) and formaldehyde-like (C2 ) isomers. The linear structure H-C-N-H+ is predicted to lie lower by 3.0 eV. Thus, the properties of the H2CN+ ion are expected to be rather similar to those of acetylene. For the vibrational frequencies, this similarity is demonstrated theoretically. The implications of these results for interstellar chemistry are discussed, including the intriguing possibility that H2CN + may be the precursor of the tentatively identified (90.665 GHz) HNC molecule. The surprisingly high observed DCN/HCN ratio is also discussed. The J = 0 J = 1 rotational transition is predicted to occur at 74.8 GHz, with an expected reliability of 1.1 GHz. Subject headings: line identifications - molecules, interstellar - quantum mechanics - radio lines - spectra, molecular