The Formation of Complex Interstellar Molecules

  • A. Dalgarno
Part of the Physics of Atoms and Molecules book series (PAMO)

Abstract

A rich array of complex molecules has been detected in interstellar space. Table 1 is a list arranged in order by the number of atoms contained in the molecule. For the complex organic species the abundances relative to hydrogen are of the order 10−8∓1010 or less. The abundances vary from one interstellar cloud to another. In TMC-1 there are observed high abundances of cyanopolyynes and complex hydrocarbons, whereas in SGR B2 oxygen-bearing organic molecules appear to be relatively enhanced. In the Orion molecular cloud, large variations occur which are associated with high velocity outflows from embedded young stars. Various attempts have been made to construct theoretical models of the formation and destruction of interstellar molecules. We review them here with particular reference to molecular species containing several carbon atoms.

Keywords

Dust Sulphide Recombination Hydrocarbon Carbon Monoxide 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Allamandola, L.J., Tielens, A.G.G.M. and Barker, J.R., 1985, Polycyclic aromatic hydrocarbons and the unidentified infrared emission bands:Auto exhaust along the Milky Way. Astrophys.J.Lett. 290, L25.ADSCrossRefGoogle Scholar
  2. Bates, D.R., 1986, Products of dissociative recombination of polyatomic ions. Astrophys.J.Lett. 306. L45.ADSCrossRefGoogle Scholar
  3. Bates, D.R., 1987, Interstellar clouds chemistry revisited in Recent Studies in Atomic and Molecular Processes (ed. A,E. Kingston) Plenum Press, London.Google Scholar
  4. Bates, D.R., 1950, Dissociative recombination. Phys.Rev. 78, 492.ADSCrossRefGoogle Scholar
  5. Boland, W. and de Jong, T., 1980, Carbon depletion in turbulent molecular cloud cores. Astrophys.J. 261, 110.ADSCrossRefGoogle Scholar
  6. Brown, R.D. and Rice, E.H.N., 1986, Galactochemistry - 1. Influence of initial conditions on predicted abundances. Mon.Not.Roy.Astro.Soc. 223, 405.Google Scholar
  7. Buch, V., Lepp, S. and Dalgarno, A., 1987, in preparation.Google Scholar
  8. Charnley, S.B., Dyson, J.E., Hartquist, T.W. and Williams, D.A., 1987, Theoretical models of mass loaded flows: II. The chemistry in TTauri wind blown bubbles in dense molecular clouds. Mon.Not.Roy.Soc. in press.Google Scholar
  9. Clary, D.C., Smith, D. and Adams, N.G., 1985, Temperature dependence of rate coefficients for reactions of ions with dipolar molecules. Chem.Phys. Lett. 119, 320.Google Scholar
  10. Crawford, M.K., Tielens, A.G.G.M. and Allamandola, L.J., 1985, Ionized polycyclic aromatic hydrocarbons and the diffuse interstellar bands. Astrophys.J.Lett. 293, L45.ADSCrossRefGoogle Scholar
  11. Dalgarno, A., 1970, Theory of ion-molecule collisions in ion-molecule reactions. E.W. McDaniel, V. Cermak, A. Dalgarno, E.E. Ferguson and L. Friedman Wiley, New York.Google Scholar
  12. de Jong, T., Dalgarno, A. and Boland, W., 1980, Hydrostatic models of molecular clouds 1. Steady state models. Astron. Ap. 91, 68.ADSGoogle Scholar
  13. d’Hendecourt, L.B., Allamandola, L.J. and Greenberg, J.M., 1985, Time-dependend chemistry in dense interstellar clouds 1. Grain surface reactions, gas/grain interactions and infrared spectroscopy. Astron.Ap. 152, 130.Google Scholar
  14. d’Hendecourt, L.R., Leger, A., Olofson, G. and Schmidt, W., 1986, The red rectangle: a possible case of visible luminescence from polycyclic aromatic hydrocarbons. Astron.Ap. 170, 91.ADSGoogle Scholar
  15. Geballe, T.R., 1986, Absorption by solid and gaseous CO towards obscured infrared objects. Astron.Ap. 162, 248.ADSGoogle Scholar
  16. Gerola, H. and Glassgold, A.E., 1978, Molecular evolution of contracting clouds: basic methods and initial results. Astrophys.J.Suppl. 37, 1.ADSCrossRefGoogle Scholar
  17. Graedel, T.E., Langer, W.D. and Frerking, M.A., 1982, The kinetic chemistry of dense interstellar clouds. Astrophys.J.Suppl. 48, 321.ADSCrossRefGoogle Scholar
  18. Green, S. and Herbst, E., 1979, Metastable isomers: a new class of interstellar molecules. Astrophys.J. 229, 121.ADSCrossRefGoogle Scholar
  19. Henning, K., 1981, Molecular formation in interstellar clouds by gas phase reactions. Astron. Ap. Suppl. 44, 405.Google Scholar
  20. Herbst, E., 1978, What are the products of polyatomic ion-electron dissociative recombination reactions? Astrophys. J. 222, 508.ADSCrossRefGoogle Scholar
  21. Herbst, E., 1983, Ion-molecule synthesis of interstellar molecular hydrocarbons through C4H: toward molecular complexity. Astrophys. J. Suppl. 53, 41.Google Scholar
  22. Herbst, E., 1987, Can gas phase reactions produce complex oxygen-containing molecules in dense interstellar clouds? A revision of some important radiative association rate coefficients. Astrophys. J. in press.Google Scholar
  23. Herbst, E. and Leung, C.M., 1986a, Synthesis of complex molecules in dense interstellar clouds in a gas-phase chemistry: model update and sensitivity analysis. Mon.Not.Roy.Astron.Soc. 222, 689.ADSGoogle Scholar
  24. Herbst, E. and Leung, C.M., 1986b, Effects of large rate coefficients for ion-polar neutral reactions on chemical models of dense interstellar clouds. Astrophys. J. 310, 378.Google Scholar
  25. Huntress, W.T. and Mitchell, G.F., 1979, The synthesis of complex molecules in interstellar clouds. Astrophys. J. 208, 237.Google Scholar
  26. Iglesias, E., 1977, The chemical evolution of molecular clouds. Astrophys.J. 218, 697.ADSCrossRefGoogle Scholar
  27. Keene, J., Blake, G.A., Phillips, T.G., Huggins, P.J. and Buchman, C.A., 1985, The abundance of atomic carbon near the ionization fronts in M17 and 5140. Astrophys. J. 299, 967.Google Scholar
  28. Knight, J.S., Freeman, C.G., McEwan, M.J., Smith, S.C., Adams, N.G. and Smith, D., 1986, Production and loss of HC3N in interstellar clouds: some relevant laboratory measurements. Mon.Not.R.Astron.Soc. 219, 89.ADSGoogle Scholar
  29. Lacy, J.H., Baas, F., Allamandola, L.J., Persson, S.E., McGregor, P.J., Lonsdale, C.J., Geballe, T.R. and van de Suit, C.E.P., 4.6 micron absorption features due to solid phase CO and cyanogroup molecules towards compact infra-red sources. Astrophys. J. 276, 533.Google Scholar
  30. Langer, W.D., Graedel, T.E., Frerking, M.A. and Armentrout, P.B., 1984, Carbon and oxygen isotope fractionation in dense interstellar clouds. Astrophys. J. 277, 581.Google Scholar
  31. Larson, H.P., Davis, D.S., Black, J.H. and Fink, U., 1985, Interstellar absorption features towards the compact infrared source W33A. Astrophys. J. 299, 873.Google Scholar
  32. Leger, A. and d’Hendecourt, L., 1985, Are polycyclic aromatic hydrocarbons the carriers of the diffuse interstellar bands in the visible? Astron. Ap. 146, 81.Google Scholar
  33. Leger, A., Jura, M. and Omont, A., 1985, Desorption from interstellar grains. Astron. Ap. 144, 147.Google Scholar
  34. Leger, A. and Puget, J.L., 1984, Identification of the unidentified IR emission features of interstellar dust? Astron. Ap. 137, L5.ADSGoogle Scholar
  35. Lepp, S. and Dalgarno, A., 1987, Polycyclic aromatic hydrocarbons in interstellar chemistry. Astrophys. J. submitted.Google Scholar
  36. Lepp, S., Dalgarno, A. and Sternberg, A., 1987, The abundance of H3+ in dense interstellar clouds. Astrophys. J. submitted.Google Scholar
  37. Leung, C.M., Herbst, E. and Huebner, W.F., 1984, Synthesis of complex molecules in dense interstellar clouds via gas-phase chemistry: a pseudo time-dependent calculation. Astrophys. J. Supp1. 56, 231.ADSCrossRefGoogle Scholar
  38. Marquette, J.B., Rowe, B.R., Dupeyrat, G., Poissant, G. and Rebrion, C., 1985, Ion polar molecule reactions: a CRESU study of He+, C+, N+ + H2O, NH at 27, 68 and 163K. Chem. Phys. Lett. 122, 431.Google Scholar
  39. Millar, T.J., Adams, N.G., Smith, D. and Clary, D.C., 1985, The HCS+/CS abundance ratio in interstellar clouds. Mon.Not.R.Astron.Soc. 216, 1025.ADSGoogle Scholar
  40. Millar, T.J. and Freeman, A., 1984, Chemical modelling of molecular sources. I.. TMC-1. Mon.Not.Roy.Astron.Soc. 207, 405; II. L183 ibid 207, 425.ADSGoogle Scholar
  41. Millar, T.J., Leung, C.M. and Herbst, E., 1987, How abundant are complex interstellar molecules? Astron. Ap. in press.Google Scholar
  42. Millar, T.J. and Nejad, L.A.M., 1985, Chemical modelling of molecular sources. IV. Time-dependent chemistry of dark clouds. Mon.Not. Roy.Astron.Soc. 217, 507.Google Scholar
  43. Mitchell, G.F. and Huntress, W.T., 1979, Long chain carbon molecules and diffuse interstellar bands. Nature 278, 722.ADSCrossRefGoogle Scholar
  44. Mitchell, G.F., Huntress, W.T. and Prasad, S.S., 1979, Interstellar synthesis of the cyanopolyynes and related molecules. Astrophys. J. 233, 102.Google Scholar
  45. Omont, A., 1986, Physics and chemistry of interstellar polycyclic aromatic molecules. Astron. Ap. 164, 159.Google Scholar
  46. Oppenheimer, M. and Dalgarno, A., 1975, The formation of carbon monoxide and the thermal balance in interstellar clouds. Astrophys. J. 200, 419.Google Scholar
  47. Prasad, S.S. and Huntress, W.T., 1980b, A model for gas phase chemistry in interstellar clouds. II. Non-equilibrium effects and effects of temperature and activation energies. Astrophys. J. 239, 151.Google Scholar
  48. Prasad, S.S. and Huntress, W.T., 1980a, A model for gas phase chemistry in interstellar clouds. 1. The basic model, library of chemical reactions and chemistry among C, N and 0 compounds. Astrophys. J. Suppl. 43, 1.Google Scholar
  49. Prasad, S.S. and Tarafdar, S.P., 1983, UV radiation field inside dense clouds: its possible existence and chemical implications. Astrophys. J. 267, 403.ADSCrossRefGoogle Scholar
  50. Smith, D., 1987, Interstellar molecules. Phil.Trans.Roy.Soc.Lond. in press.Google Scholar
  51. Sternberg, A., Dalgarno, A. and Lepp, S., 1987, Cosmic ray induced photodestruction of interstellar molecules in dense clouds. Astrophys.J. submitted.Google Scholar
  52. Su, T. and Bowers, M.I., 1979, Classical ion-molecule collision theory, p. 84 in Gas phase ion chemistry (ed. M.T. Bowers) Academic, New York.Google Scholar
  53. Takayanagi, K., 1978, Low energy ion-polar molecule collisions - the perurbed rotational state approach. J.Phys.Soc. Japan 45, 976.Google Scholar
  54. Tarafdar, S.P., Prasad, S.S., Huntress, W.T., Villere, K.R. and Black, D.C., 1985, Chemistry in dynamically cooling clouds. Astrophys. J. 289, 220.Google Scholar
  55. Van der Zwet, G.P. and Allamandola, L.J., 1985, Polycyclic aromatic hydrocarbons and the diffuse interstellar bands. Astron. Ap. 146, 76.Google Scholar
  56. Watt, G.D., 1983, Time-dependent chemistry - 1. Modelling of a static cloud.Mon.Not.Roy.Astron.Soc. 205, 21.ADSGoogle Scholar
  57. Watt, G.D., 1985, Time-dependent chemistry - II. Dependence of the chemistry on the initial [C] - CO] ratio. Mon.Not.R.Astron.Soc. 212, 93.Google Scholar
  58. Whittet, D.C.B., Longmore, A.J. and McFadzean, A.D., 1985, Solid CO in the Taurus dark clouds. Mon.Not.Roy.Astron.Soc. 216, 45 P.ADSGoogle Scholar
  59. Williams, D.A., 1985, On the abundance of molecular hydrogen in the galaxy. Q.Jl.Roy.Astron.Soc. No. 4, vol. 26, 463.Google Scholar
  60. Williams, D.A. and Hartquist, T.W., 1984, on C° and CO in dense interstellar clouds - evidence that cloud material is frequently shocked. Mon. Not.Roy.Soc. 210, 141.Google Scholar

Copyright information

© Plenum Press, New York 1987

Authors and Affiliations

  • A. Dalgarno
    • 1
  1. 1.Harvard-Smithsonian Center for AstrophysicsCambridgeUSA

Personalised recommendations