Infrared emission spectra of candidate interstellar aromatic molecules

Article metrics

Abstract

INTERSTELLAR dust is responsible, through surface reactions, for the creation of molecular hydrogen, the main component of the interstellar clouds in which new stars form. Intermediate between small, gas-phase molecules and dust are the polycyclic aromatic hydrocarbons (PAHs). Such molecules could account for 2–30% of the carbon in the Galaxy1, and may provide nucleation sites for the formation of carbonaceous dust2,3. Although PAHs have been proposed4,5 as the sources of the unidentified infrared emission bands that are observed in the spectra of a variety of interstellar sources6–11, the emission characteristics of such molecules are still poorly understood. Here we report laboratory emission spectra of several representative PAHs, obtained in conditions approximating those of the interstellar medium, and measured over the entire spectral region spanned by the unidentified infrared bands. We find that neutral PAHs of small and moderate size can at best make only a minor contribution to these emission bands. Cations of these molecules, as well as much larger PAHs and their cations, remain viable candidates for the sources of these bands.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.

from$8.99

All prices are NET prices.

References

  1. 1

    Snow, T. P. & Witt, A. N. Science 270, 1455–1460 (1995).

  2. 2

    Tielens, A. G. G. M. in Carbon in the Galaxy: Studies From Earth and Space (eds Tarter, J. C., Chan, S. & DeFrees, D. J.) 59–111 (NASA Conf. Publ. 3061, Moffett Field, 1987).

  3. 3

    Cadwell, B. J., Wang, H., Feigelson, E. D. & Frenklach, M. Astrophys. J. 429, 285–299 (1994).

  4. 4

    Allamandola, L. J., Tielens, A. G. G. M. & Barker, J. R. Astrophys. J. Suppl. Ser. 71, 733–775 (1989).

  5. 5

    Léger, A. & d'Hendecourt, L. Ann. Phys. Fr. 14, 181–206 (1989).

  6. 6

    Cohen, M. et al. Astrophys. J. 341, 246–269 (1989).

  7. 7

    Geballe, T. R., Lacy, J. H., Persson, S. E., McGregor, P. J. & Soifer, B. T. Astrophys. J. 292, 500–505 (1985).

  8. 8

    Witteborn, F. C. et al. Astrophys. J. 341, 270–277 (1989).

  9. 9

    de Muizon, M. J., d'Hendecourt, L. B. & Geballe, T. R. Astr. Astrophys. 235, 367–378 (1990).

  10. 10

    Schutte, W. A., Tielens, A. G. G. M., Allamandola, L. J., Cohen, M. & Wooden, D. H. Astrophys. J. 360, 577–589 (1990).

  11. 11

    Allamandola, L. J. et al. Astrophys. J. 345, L59–L62 (1989).

  12. 12

    Petroff, M. D., Stapelbroek, M. G. & Kleinhans, W. A. Appl. Phys. Lett. 51, 406–408 (1987).

  13. 13

    Schlemmer, S. et al. Science 265, 1686–1689 (1994).

  14. 14

    Allamandola, L. J., Tielens, A. G. G. M. & Barker, J. R. Astrophys. J. 290, L25–L28 (1985).

  15. 15

    Léger, A. & Puget, J. L. Astr. Astrophys. 137, L5–L8 (1984).

  16. 16

    Shan, J., Suto, M. & Lee, L. C. Astrophys. J. 383, 459–465 (1991).

  17. 17

    Williams, R. M. & Leone, S. R. Astrophys. J. 443, 675–681 (1995).

  18. 18

    Flickinger, G. C., Wdowiak, T. J. & Gómez, P. L. Astrophys. J. 380, L43–L46 (1991).

  19. 19

    Joblin, C., d'Hendecourt, L., Léger, A. & Défourneau, D. Astr. Astrophys. 281, 923–936 (1994).

  20. 20

    Joblin, C., Boissel, P., Léger, A., d'Hendecourt, L. & Défourneau, D. Astr. Astrophys. 299, 835–846 (1995).

  21. 21

    Allamandola, L. J., Sandford, S. A., Hudgins, D. M. & Witteborn, F. C. in Airborne Astronomy Symposium on the Galactic Ecosystem (eds Haas, M. R., Davidson, J. A. & Erickson, E. F.) 23–32 (Astronomical Soc. of the Pacific, San Francisco, 1995).

  22. 22

    Hudgins, D. M. & Allamandola, L. J. J. phys. Chem. 99, 3033–3046 (1995).

  23. 23

    Szczepanski, J. & Vala, M. Astrophys. J. 414, 646–655 (1993).

  24. 24

    Szczepanski, J., Chapo, C. & Vala, M. Chem. Phys. Lett. 205, 434–439 (1993).

  25. 25

    Vala, M. et al. J. phys. Chem. 98, 9187–9196 (1994).

  26. 26

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

  27. 27

    Langhoff, S. R. J. phys. Chem. (in the press).

  28. 28

    Brenner, J. & Barker, J. R. Astrophys. J. 388, L39–L43 (1992).

  29. 29

    Cherchneff, I. & Barker, J. R. Astrophys. J. 341, L21–L24 (1989).

Download references

Author information

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Cook, D., Schlemmer, S., Balucani, N. et al. Infrared emission spectra of candidate interstellar aromatic molecules. Nature 380, 227–229 (1996) doi:10.1038/380227a0

Download citation

Further reading

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.