Hostname: page-component-6bf8c574d5-zc66z Total loading time: 0 Render date: 2025-03-07T08:47:53.463Z Has data issue: false hasContentIssue false
  • English
  • Français

Chemical Evolution of Dense Clouds

Published online by Cambridge University Press:  14 August 2015

E. W. Chapelle ,
B. D. Donn ,
W. A. Payne Jr.  and
L. J. Stief
E. W. Chapelle
Affiliation:
Astrochemistry Branch, Laboratory for Extraterrestrial Physics, NASA/Goddard Space Flight Center, Greenbelt, Md. 20771, U.S.A.
B. D. Donn
Affiliation:
Astrochemistry Branch, Laboratory for Extraterrestrial Physics, NASA/Goddard Space Flight Center, Greenbelt, Md. 20771, U.S.A.
W. A. Payne Jr.
Affiliation:
Astrochemistry Branch, Laboratory for Extraterrestrial Physics, NASA/Goddard Space Flight Center, Greenbelt, Md. 20771, U.S.A.
L. J. Stief
Affiliation:
Astrochemistry Branch, Laboratory for Extraterrestrial Physics, NASA/Goddard Space Flight Center, Greenbelt, Md. 20771, U.S.A.

Abstract

Core share and HTML view are not available for this content. However, as you have access to this content, a full PDF is available via the ‘Save PDF’ action button.

Thermal reactions largely determine the chemical evolution of interstellar molecules during various phases associated with the evolution of interstellar clouds. A similar mechanism may be the source of the array of observed polyatomic molecules. If astronomical time scales are comparable to or less than chemical time scales, thermodynamic equilibrium will not be attained. Other factors also affect the validity of thermodynamic calculations of molecular composition. An experimental investigation of thermal reactions in a simplified system is under way. Preliminary results of the HCN–H2 reaction at 1000 K indicate reaction times of several hours. These have been extrapolated to lower temperatures and fitted to models of the primordial solar nebula, proto stars and red giants. In these situations equilibrium would generally not be attained and reaction products would freeze out at temperatures near 700 K or greater.

Type
Part VII Molecules, Theory and Observations
Information
Symposium - International Astronomical Union , Volume 52: Interstellar Dust and Related Topics , 1973 , pp. 387 - 393
Copyright
Copyright © Reidel 1973 

References

Anders, E.: 1971, Ann. Rev. Astron. Astrophys. 9, 1.CrossRefGoogle Scholar
Bahn, G. S.: 1968, Reaction Rate Compilation for the H–O–N System , Gordon and Breach, N.Y.Google Scholar
Barrett, A. H., Schwartz, R. P., and Waters, J. W.: 1971, Astrophys. J. 168, L101.Google Scholar
Calvin, M.: 1968, Chemical Evolution , Oxford University Press, N.Y.Google Scholar
Cameron, A. G. W.: 1969, in Kuman, S. S. (ed.), Low Luminosity Stars , Gordon and Breach, N.Y., p. 423.Google Scholar
Cameron, A. G. W.: 1972, preprint submitted to Icarus.Google Scholar
Kaplan, S. A. and Pikel'ner, S. B.: 1970, The Interstellar Medium , Harvard Univ. Press. Cambridge, Mass. Google Scholar
Kondratiev, V. N.: 1972, in Fiestrom, R. M. (ed.), Rate Constants of Gas Phase Reactions-Reference Book (transl. by Holtschlag, L. J.), Office Standard Reference Data, N.B.S., National Technical Information Service, Washington, D.C., U.S.A. Google Scholar
Larimer, J. W.: 1967, Geochim. Cosmochim. Acta 31, 1215.Google Scholar
Lewis, J. S.: 1972, Icarus 16, 241.Google Scholar
Liège Astrophysics Symposium : 1970, ‘Stellar Evolution before the Main Sequence’, see particularly introductory reports and references, Univ. of Liege, 1970.Google Scholar
Lord, H. C.: 1965, Icarus 4, 279.Google Scholar
Oro, J.: 1965, in Fox, S. W. (ed.), The Origin of Prebiological Systems , Academic Press, N.Y., p. 137.Google Scholar
Penzias, A. A., Solomon, P. M., Wilson, R. W., and Jefferts, K. B.: 1971, Astrophys. J. 168, L53.Google Scholar
Sagan, C.: 1965, in Fox, S. W. (ed.), The Origin of Prebiological Systems , see discussion following paper by Oro, p. 102, Academic Press, N.Y. Google Scholar
Savronov, V. S.: 1964, Techtonophysics 1, 217.CrossRefGoogle Scholar
Savronov, V. S. (1966) Soviet Astron. AJ 9, 987.Google Scholar
Shimizu, M.: 1973, Prog. Theor. Phys. 49, 153.Google Scholar
Snyder, L. E. and Buhl, D.: 1971, Astrophys. J. 163, L47.Google Scholar
Tsuji, T.: 1964, Ann. Tokyo Astron. Obs. 9, 1.Google Scholar
Urey, H. C.: 1952, The Planets , Yale Univ. Press, New York.Google Scholar