Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Role of different isomers of the H2CN+ ion in the formation of interstellar HCN and HNC


THE H2CN+ molecular ion is generally agreed1–4 to have a critical role in the formation of interstellar HCN and HNC. The obvious problem that H2CN+ has not yet been identified in interstellar space is complicated by considerable uncertainty due to the possible existence of three distinct isomers of H2CN+, with nuclear arrangements Brown4 stated that although the third isomer had been completely neglected in previous discussion, it is likely to have a crucial role in the formation of HNC. Brown also notes that the linear isomer, which is isoelectronic with acetylene and thus expected to lie lowest of all the isomers of H2CN+, may play no part at all in the formation of either HCN or HNC. This is from the hypothesis that the sequence thought most likely to lead to HCN is orfollowed by dissociative recombinationBrown argues that the formation of the more stable linear isomer (1) would require the migration of a hydrogen atom from carbon to nitrogen. As this migration is expected to be very costly energetically, the H2CN+ on the right hand side of reactions (4) and (5) should be the isomer (2) above. Similarly, he argues that the sequence leading to HNC should exclusively involve isomer (3). We report here theoretical studies designed to investigate the molecular structure of (3) and its energy relative to the previously studied3 isomers (1) and (2). In addition, because reactions (4), (5) and (7) must be exothermic or very nearly so if they play a part in the interstellar medium, this question has also been assessed.

This is a preview of subscription content, access via your institution

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.


  1. Herbst, E. & Klemperer, W. Astrophys. J. 185, 505 (1973).

    Article  ADS  CAS  Google Scholar 

  2. Watson, W. D. Astrophys. J. Lett. 183, L17 (1973).

    Article  ADS  CAS  Google Scholar 

  3. Pearson, P. K. & Schaefer, H. F. Astrophys. J. 192, 33 (1974).

    Article  ADS  CAS  Google Scholar 

  4. Brown, R. D. Nature 270, 39 (1977).

    Article  ADS  CAS  Google Scholar 

  5. Dunning, T. H. J. chem. Phys. 53, 2823 (1970).

    Article  ADS  CAS  Google Scholar 

  6. Schaefer, H. F. The Electronic Structure of Atoms and Molecules: A Survey of Rigorous Quantum Mechanical Results (Addison-Wesley, Reading, Massachusetts, 1972).

    Google Scholar 

  7. Pulay, P. in Modern Theoretical Chemistry, Vol. 4 (ed. Schaefer, H. F.) (Plenum, New York, 1977).

    Google Scholar 

  8. Lucchese, R. R. & Schaefer, H. F. J. chem. Phys. 68, 769 (1978).

    Article  ADS  CAS  Google Scholar 

  9. Liddy, J. P., Freeman, C. G. & McEwan, M. J. Mon. Not. R. astr. Soc. 180, 683 (1977).

    Article  ADS  CAS  Google Scholar 

  10. JANAF Thermochemical Tables, 2nd edn (NBS Washington, D.C., 1971).

  11. Herzberg, G. Electronic Spectra of Polyatomic Molecules (Van Nostrand Reinhold, New York, 1966).

    Google Scholar 

  12. Moore, C. E. Atomic Energy Levels (NBS Washington, D.C., 1949).

    Google Scholar 

  13. Wolf, J. F. et al. J. Am. chem. Soc. 99, 5417 (1977).

    Article  CAS  Google Scholar 

  14. Smith, D. & Adam, N. G. Chem. phys. Lett. 47, 145 (1977).

    Article  ADS  CAS  Google Scholar 

  15. Fehsenfeld, F. C. Astrophys. J. 209, 638 (1976).

    Article  ADS  CAS  Google Scholar 

Download references

Author information

Authors and Affiliations


Rights and permissions

Reprints and Permissions

About this article

Cite this article

CONRAD, M., SCHAEFER, H. Role of different isomers of the H2CN+ ion in the formation of interstellar HCN and HNC. Nature 274, 456–457 (1978).

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI:


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing