Skip to main content

Thank you for visiting nature.com. 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.

  • Letter
  • Published:

The interstellar chemistry of PAH cations

Nature volume 391, pages 259–260 (1998)Cite this article

Abstract

Diffuse interstellar bands (DIBs) are mysterious absorption lines in the optical spectra of stars, and have been known for 75 years1. Although it is widely believed2,3,4 that they arise from gas-phase organic molecules (rather than from dust grains) in the interstellar medium, no consensus has been reached regarding their precise cause. The realization that many emission features in astronomical infrared spectra probably arise from polycyclic aromatic hydrocarbons5,6,7,8 (PAHs), which may themselves be very abundant in the interstellar medium, has led to the suggestion that ionized PAHs might be the source of the DIBs9,10,11,12. Laboratory investigations have revealed that small, positively charged PAHs in matrices have absorption features that bear some resemblance to DIBs13,14,15, but no clear identification of any DIB with any specific PAH cation has yet been made. Here we report a laboratory study of the chemical reactivity of PAH cations (C6H6+, C10H8+and C16H10+) in the gas phase. We find that these PAH cations are very reactive, and are therefore unlikely to survive in high abundances in the interstellar medium. Rather, such molecules will react rapidly with hydrogen, and we therefore suggest that the resulting protonated PAH cations (and species derived from them) should become the focus of future searches for a correspondence between molecular absorption features and the DIBs.

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

Access options

Buy this article

  • Purchase on Springer Link
  • Instant access to full article PDF
Buy now

Prices may be subject to local taxes which are calculated during checkout

Similar content being viewed by others

References

  1. Heger, M. L. The spectra of certain class B stars in the regions 5630 å–6680 å and 3280 å–3380 å. Lick Obs. Bull. 10, 146–147 (1922).

    ADS  Google Scholar 

  2. Tielens, A. G. G. M. & Snow, T. P. (eds) The Diffuse Interstellar Bands (Kluwer, Dordrecht, (1995)).

    Book  Google Scholar 

  3. Herbig, G. H. The diffuse interstellar bands. Annu. Rev. Astron. Astrophys. 33, 19–73 (1995).

    Article  ADS  CAS  Google Scholar 

  4. Snow, T. P. in From Stardust to Planetesimals (eds Pendleton, Y. J. & Tielens, A. G. G. M.) 147–157 (Astron. Soc. Pacific, San Francisco, (1997)).

    Google Scholar 

  5. Léger, A. & Puget, J. Identification of the “unidentified” IR emission features of interstellar dust? Astron. Astrophys. 137, L5–L8 (1984).

    ADS  Google Scholar 

  6. Allamandola, L. J., Tielens, A. G. G. M. & Barker, J. R. Polycyclic aromatic hydrocarbons and the unidentified infrared emission bands: auto exhaust along the Milky Way! Astrophys. J. 290, L25–L28 (1985).

    Article  ADS  CAS  Google Scholar 

  7. Puget, J. & Léger, A. Anew component of the interstellar matter: small grains and large aromatic molecules. Annu. Rev. Astron. Astrophys. 27, 161–198 (1989).

    Article  ADS  CAS  Google Scholar 

  8. Allamandola, L. J., Tielens, A. G. G. M. & Barker, J. R. Interstellar polycyclic aromatic hydrocarbons: the infrared emission bands, the excitation/emission mechanism, and the astrophysical implications. Astrophys. J. Suppl. 71, 733–775 (1989).

    Article  ADS  CAS  Google Scholar 

  9. Crawford, M. K., Tielens, A. G. G. M. & Allamandola, L. J. Ionized polycyclic aromatic hydrocarbons and the diffuse interstellar bands. Astrophys. J. 293, L45–L48 (1985).

    Article  ADS  CAS  Google Scholar 

  10. Léger, A. & d'Hendecourt, L. Are polycyclic aromatic hydrocarbons the carriers of the diffuse interstellar bands in the visible? Astron. Astrophys. 146, 81–85 (1985).

    ADS  Google Scholar 

  11. van der Zwet, G. P. & Allamandola, L. J. Polycyclic aromatic hydrocarbons and the diffuse interstellar bands. Astron. Astrophys. 146, 76–80 (1985).

    ADS  CAS  Google Scholar 

  12. Salama, F., Bakes, E. L. O., Allamandola, L. J. & Tielens, A. G. G. M. Assessment of the polycyclic aromatic hydrocarbon — Diffuse interstellar band proposal. Astrophys. J. 458, 621–636 (1996).

    Article  ADS  CAS  Google Scholar 

  13. Salama, F. & Allamandola, L. J. The ultraviolet and visible spectrum of the polycyclic aromatic hydrocarbon C10H8+: Possible contributions to the diffuse interstellar bands and to the ultraviolet–visible extinction. Astrophys. J. 395, 301–306 (1992).

    Article  ADS  CAS  Google Scholar 

  14. Salama, F. & Allamandola, L. J. Is a pyrene-like molecular ion the cause of the 4430 å diffuse interstellar absorption band? Nature 358, 42–43 (1992).

    Article  ADS  CAS  Google Scholar 

  15. Léger, A., d'Hendecourt, L. & Défourneau, D. Proposed identification for the (common) carriers of the 4430 å and 7565 å DIBs. Astron. Astrophys. 293, L53 (1995).

    ADS  Google Scholar 

  16. Van Doren, J. M., Barlow, S. E., DePuy, C. H. & Bierbaum, V. M. The tandem flowing-afterglow-SIFT-drift. Int. J. Mass Spectrom. Ion Processes 81, 85–100 (1987).

    Article  ADS  CAS  Google Scholar 

  17. Howorka, F. Reactions of singly and doubly charged argon ions with N2and O2in a steady state hollow cathode discharge. J. Chem. Phys. 68, 804–811 (1978).

    Article  ADS  CAS  Google Scholar 

  18. Savage, B. D. & Sembach, K. R. Interstellar abundances from absorption-line observations with the Hubble Space Telescope. Annu. Rev. Astron. Astrophys. 34, 279–329 (1996).

    Article  ADS  CAS  Google Scholar 

  19. Petrie, S., Javahery, G. & Bohme, D. K. Gas-phase reactions of benzenoid hydrocarbons and ions with hydrogen atoms and molecules: Uncommon constraints to reactivity. J. Am. Chem. Soc. 114, 9205–9206 (1992).

    Article  CAS  Google Scholar 

  20. Scott, G. B. I. et al. CmHn+ reactions with H and H2: An experimental study. J. Phys. Chem. 101, 4973–4978 (1997).

    Article  CAS  Google Scholar 

  21. Tosi, P. et al. The reaction of CO2+ with atomic hydrogen. J. Chem. Phys. 80, 1905–1906 (1984).

    Article  ADS  CAS  Google Scholar 

  22. Setser, D. W. (ed.) Reactive Intermediates in the Gas Phase (Academic, New York, (1979)).

    Google Scholar 

  23. de Petris, G., Occhiucci, G. & Pepi, F. Amass spectrometric study of gaseous H4PO3+ and H2PO3− ions. Int. J. Mass Spectrom. Ion Processes 136, 155–166 (1994).

    Article  ADS  CAS  Google Scholar 

  24. Giles, K., Adams, N. G. & Smith, D. Astudy of reactions of CnHm+ ions (n = 4,5,6; m = 0–6) with H2and CO at 300 K and 80 K. Int. J. Mass Spectrom. Ion Processes 89, 303–317 (1989).

    Article  ADS  CAS  Google Scholar 

  25. Le Page, V., Keheyan, Y., Bierbaum, V. M. & Snow, T. P. Chemical constraints on organic cations in the interstellar medium. J. Am. Chem. Soc. 119, 8373–8374 (1997).

    Article  CAS  Google Scholar 

  26. Snow, T. P. & Witt, A. N. The interstellar carbon budget and the role of carbon in dust and large molecules. Science 270, 1455–1460 (1995).

    Article  ADS  CAS  Google Scholar 

  27. Abouelaziz, H., Gomet, J. C., Pasquerault, D. & Rowe, B. R. Measurements of C3H3+, C5H3+, C6H6+, C7H5+, and C10H8+ dissociative recombination rate coefficients. J. Chem. Phys. 99, 237–243 (1993).

    Article  ADS  CAS  Google Scholar 

  28. Adamson, A. J., Whittet, D. C. B. & Duley, W. W. Diffuse interstellar bands in the Taurus dark clouds. Mon. Not. R. Astron. Soc. 252, 234–245 (1991).

    Article  ADS  CAS  Google Scholar 

  29. Snow, T. P., Bakes, E. L. O., Buss, R. H. & Seab, C. G. The weakness of diffuse bands in nebular environments: Possible impact on the PAH+ hypothesis. Astron. Astrophys. 296, L37–L40 (1995).

    ADS  CAS  Google Scholar 

  30. Le Page, V., Bierbaum, V. M., Keheyan, Y. & Snow, T. P. Astudy of reactions of cations derived from naphthalene with molecules and atoms of interstellar interest. J. Am. Chem. Soc.(submitted).

  31. Allain, T., Leach, S. & Sedlmayr, E. Photodestruction of PAHs in the interstellar medium. I. Photodissociation rates for the loss of an acetylenic group. Astron. Astrophys. 305, 602–615 (1996).

    ADS  CAS  Google Scholar 

  32. Omont, A. Astron. Astrophys. 164, 159–178 (1986).

    Google Scholar 

Download references

Acknowledgements

This research has been supported by a NASA grant to the University of Colorado.

Author information

Authors and Affiliations

  1. Center for Astrophysics and Space Astronomy, University of Colorado, Campus Box 389, Boulder, 80309, Colorado, USA

    Theodore P. Snow

  2. Department of Chemistry and Biochemistry, University of Colorado, Campus Box 215, Boulder, 80309, Colorado, USA

    Valery Le Page & Veronica M. Bierbaum

  3. Istituto di Chimica Nucleare del CNR, Monterotondo Stazione, 00016, Roma, Italy

    Yeghis Keheyan

Authors
  1. Theodore P. Snow
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Valery Le Page
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Yeghis Keheyan
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Veronica M. Bierbaum
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Theodore P. Snow.

Rights and permissions

Reprints and permissions

About this article

Cite this article

Snow, T., Le Page, V., Keheyan, Y. et al. The interstellar chemistry of PAH cations. Nature 391, 259–260 (1998). https://doi.org/10.1038/34602

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI: https://doi.org/10.1038/34602

This article is cited by

Comments

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.

Search

Advanced search

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