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Formation of Molecular Hydrogen in Interstellar Space1

Published online by Cambridge University Press:  08 February 2017

H. F. P. Knaap ,
C. J. N. Van Den Meijdenberg ,
J. J. M. Beenakker  and
H. C. Van De Hulst
H. F. P. Knaap
Affiliation:
Leiden University, Leiden, The Netherlands
C. J. N. Van Den Meijdenberg
Affiliation:
Leiden University, Leiden, The Netherlands
J. J. M. Beenakker
Affiliation:
Leiden University, Leiden, The Netherlands
H. C. Van De Hulst
Affiliation:
Leiden University, Leiden, The Netherlands

Extract

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Although Several Attempts at observing the interstellar hydrogen molecules in the ultraviolet or infrared are in preparation (ref. 1), these molecules are still undetected. They may form the most abundant unobserved constituent of the interstellar gas. The strongest indirect argument for the presence of these molecules lies in the fact that the density of atomic hydrogen observed by the 21-cm line goes down in some dark clouds, where the dust density and, presumably, the total gas density goes up by a large factor.

Inasmuch as the density in the interstellar clouds is of the order of 10 atoms/cm3 and the temperature is only of the order of 100° K, any formation of molecules by atom-atom collisions is too slow to be of importance. The most eligible process for H2 formation is recombination on the surface of an interstellar dust grain. Rate estimates of this process have been made in various degrees of detail, as reported in references 2 to 4.

Type
Research Article
Information
International Astronomical Union Colloquium , Volume 7: Proper Motions , August 1965 , pp. 253 - 257
Copyright
Copyright © Kluwer Academic Publishers 1965

Footnotes

1

The contents of this paper were published previously in the Bull, of the Astron. Inst, of the Netherlands, vol. 18, 1966, pp. 256-258.

References

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