Space Science Reviews

, Volume 106, Issue 1–4, pp 73–86 | Cite as

Deuterium Fractionation in Interstellar Clouds

  • T. J. Millar


This paper reviews the chemical processes responsible for fractionating deuterium in interstellar molecules. I show that this process is intrinsically a low temperature phenomenon and discuss how the degree of enhancement of the deuterium content of molecules is related to the physical conditions, particularly abundances, in molecular clouds. If significant amounts of abundant species, such as CO, are frozen out on to interstellar dust grains, the resulting enhancement in H2D+ can result in its abundance being greater than that of H 3 + at 10K. Transfer of the deuteron from H2D+ can then lead to the efficient formation of multiply deuterated species, such as NHD2 and ND3. Fractionation can also occur in grain surface reactions and some simple models are discussed.

deuterium interstellar clouds 


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  1. Aikawa, Y., and Herbst, E.: 2001, 'Two-Dimensional Distributions and Column Densities of Gaseous Molecules in Protoplanetary Disks. II. Deuterated Species and UV Shielding by Ambient Clouds', Astron. Astrophys. 371, 1107–1117.CrossRefADSGoogle Scholar
  2. Blake, G.A., Qi, C., Hogerheijde, M.R., Gurwell, M.A., and Muhleman, D.O.: 1999, 'Sublimation from Icy Jets as a Probe of the Interstellar Volitile Content of Comets', Nature 398, 213–216.CrossRefADSGoogle Scholar
  3. Brown, P.D., and Millar, T.J.: 1989, 'Grain Surface Formation of Multi-Deuterated Molecules', Month. Not. Roy. Astron. Soc. 240, 25P–29P.ADSGoogle Scholar
  4. Brown, P.D., Charnley, S.B., and Millar, T.J.: 1988, 'A Model of the Chemistry in Hot Molecular Cores', Month. Not. Roy. Astron. Soc. 231, 409–417.ADSGoogle Scholar
  5. Caselli, P., Hasegawa, T.I., and Herbst, E.: 1998, 'A Proposed Modification of the Rate Equations for Reactions on Grain Surfaces', Astrophys. J. 495, 309–316.CrossRefADSGoogle Scholar
  6. Caselli, P., Walmsley, C.M., Tafalla, M., Dore, L., and Myers, P. C.: 1999, 'CO Depletion in the Starless Cloud Core L1544', Astrophys. J. 523, L165–L169.CrossRefADSGoogle Scholar
  7. Caselli, P., Stantcheva, T., Shalabiea, O., Shematovich, V.I., and Herbst, E.: 2002, 'Deuterium Fractionation on Interstellar Grains Studied with Modified Rate Equations and a Monte Carlo Approach', Plan. Space Sci., in press.Google Scholar
  8. Ceccarelli, C., Castets, A., Loinard, L., Caux, E., and Tielens, A.G.G.M.: 1998, 'Detection of Doubly Deuterated Formaldehyde Towards the Low-luminosity Protostar IRAS 16293-2422', Astron. Astrophys. 338, L43–L46.ADSGoogle Scholar
  9. Charnley, S.B., Tielens, A.G.G.M., and Rodgers, S.D.: 1997, 'Deuterated Methanol in the Orion Compact Ridge', Astrophys. J. 482, L203–L206.CrossRefADSGoogle Scholar
  10. Cohen, S.D., and Hindmarsh, A.C.: 1996, 'CVODE, a Stiff/Nonstiff ODE Solver in C', Computers in Physics 10, 138–143.Google Scholar
  11. Delsemme, A.H.: 2000, '1999 Kuiper Prize Lecture: Cometary Origin of the Biosphere', Icarus 146, 313–325.CrossRefADSGoogle Scholar
  12. Gensheimer, P.D., Mauersberger, R., and Wilson, T.L.: 1996, 'Water in Galactic Hot Cores', Astron. Astrophys. 314, 281–294.ADSGoogle Scholar
  13. Gibb, A.G., and Little, L.T.: 1998, 'Probing the Structure of Molecular Cloud Cores: Observations and Modeling of CI and C18O', Month. Not. Roy. Astron. Soc. 295, 299–311.CrossRefADSGoogle Scholar
  14. Hatchell, J., Millar, T.J., and Rodgers, S.D.: 1998, 'The DCN/HCN Abundance Ratio in Hot Molecular Cores', Astron. Astrophys. 332, 695–702.ADSGoogle Scholar
  15. Jensen, M.J., Bilodeau, R.C., Safvan, C.P., Seiersen, K., Andersen, L.H., Pedersen, H.B., and Heber, O.: 2000, 'Dissociative Recombination of H3O+, HD2O+, and D3O+', Astrophys. J. 543, 764–774.CrossRefADSGoogle Scholar
  16. Larsson, M., Lepp, S., et al.: 1996, 'Dissociative Recombination of H2D+ and the Cosmic Abundance of Deuterium', Astron. Astrophys. 309, L1–L3.ADSGoogle Scholar
  17. 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. Suppl. 56, 231–256.CrossRefADSGoogle Scholar
  18. Lis, D.C., Roueff, E., Gerin, M., Phillips, T.G., Coudert, L.H., van der Tak, F.F.S., and Schilke, P.:2002, 'Detection of Triply Deuterated Ammonia in the Barnard 1 Cloud', Astrophys. J. 571, L55–L58.CrossRefADSGoogle Scholar
  19. Loinard, L., Castets, A., Ceccarelli, C., Tielens, A.G.G.M., Fauré, A., Caux, E., and Duvert, G.: 2000, 'The Enormous Abundance of D2CO in IRAS 16293-2422', Astron. Astrophys. 359, 1169–1174.ADSGoogle Scholar
  20. Millar, T.J., and Freeman, A.: 1984, 'Chemical Modelling of Molecular Sources I. TMC-1', Month. Not. Roy. Astron. Soc. 207, 405–423.ADSGoogle Scholar
  21. Mousis, O., Gautier, D., and Coustenis, A.: 2002, 'The D/H Ratio in Methane in Titan: Origin and History', Icarus 159, 156–165.CrossRefADSGoogle Scholar
  22. Roberts, H., and Millar, T.J.: 2000a, 'Modelling of Deuterium Chemistry and its Application to Molecular Clouds', Astron. Astrophys. 361, 388–398.ADSGoogle Scholar
  23. Roberts, H., and Millar, T.J.: 2000b, 'Gas-Phase Formation of Doubly-Deuterated Species', Astron. Astrophys. 364, 780–784.ADSGoogle Scholar
  24. Roberts, H., Herbst, E., and Millar, T.J.: 2002, 'The Importance of New Rate Coefficients for D Fractionation Reactions on Interstellar Chemistry', Month. Not. Roy. Astron. Soc. 336, 283–290.CrossRefADSGoogle Scholar
  25. Roberts, H., and Millar, T.J.: 2002, in preparation.Google Scholar
  26. Rodgers, S.D., and Charnley, S.C.: 2001, 'Gas-phase Production of NHD2 in L134N', Astrophys. J. 553, 613–617.CrossRefADSGoogle Scholar
  27. Rodgers, S.D., and Charnley, S.C.: 2002, 'A Model of the Chemistry in Cometary Comae: Deuterated Molecules', Month. Not. Roy. Astron. Soc. 330, 660–674.CrossRefADSGoogle Scholar
  28. Roueff, E., Tiné, S., Coudert, L. H., Pineau des Fôrets, G., Falgarone, E., and Gerin, M.: 2000, 'Detection of Doubly Deuterated Ammonia in L134N', Astron. Astrophys. 354, L63–L66.ADSGoogle Scholar
  29. Stantcheva, T., Caselli, P., and Herbst, E.: 2001, 'Modified Rate Equations Revisited. A Corrected Treatment for Diffusive Reactions on Grain Surfaces', Astron. Astrophys. 375, 673–679.ADSGoogle Scholar
  30. Stark, R., van der Tak, F.F.S., and van Dishoeck, E.F.: 1999, 'Detection of Interstellar H2D+ Emission', Astrophys. J. 521, L67–L70.CrossRefADSGoogle Scholar
  31. van der Tak, F.F.S., Schilke, P., Müller, H.S.P., Lis, D.C., Phillips, T.G., Gerin, M., and Roueff, E.: 2002, 'Triply Deuterated Ammonia in NGC 1333', Astron. Astrophys. 388, L53–L56.CrossRefADSGoogle Scholar
  32. Tiné, S., Roueff, E., Falgarone, E., Gerin, M., and Pineau des Fôrets, G.: 2000, 'Deuterium Fractionation in Dense Ammonia Cores', Astron. Astrophys. 356, 1039–1049.ADSGoogle Scholar
  33. Watson, W.D.: 1974, 'Ion-Molecule Reactions, Molecule Formation, and Hydrogen-Isotope Exchange in Dense Interstellar Clouds', Astrophys. J. 188, 35–42.CrossRefADSGoogle Scholar
  34. Williams, J.P., Bergin, E.A., Caselli, P., Myers, P.C., and Plume, R.: 1998, 'The Ionization Fraction in Dense Cloud Cores', Astrophys. J. 503, 689–699.CrossRefADSGoogle Scholar

Copyright information

© Kluwer Academic Publishers 2003

Authors and Affiliations

  • T. J. Millar
    • 1
  1. 1.Physics Department, UMISTManchesterUK

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