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Interstellar medium, molecules
Definition
Molecular line cooling is the physical process whereby de-excitation of collisionally or radiatively excited molecules leads to the emission of a photon, followed by its escape from the local cloud volume, thus cooling the local gas.
Overview
In astronomical environments where most of the hydrogen is molecular, the gas can cool through emission of the photons associated with transitions from higher to lower rotational and vibrational levels in molecules. In cold molecular clouds, the major molecular coolant is CO. In shock waves, H2, H2O, and CO dominate the molecular cooling. Other molecules that can act as relatively minor coolants are OH, HD, and CH.
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References and Further Reading
Hollenbach DJ, Thronson HA Jr (eds) (1987) Interstellar processes. D. Reidel, Dordrecht
Kwok S (2007) Physics and chemistry of the interstellar medium. University Science, Herndon
Tielens AGM (2005) The physics and chemistry of the interstellar medium. Cambridge University Press, Cambridge
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© 2011 Springer-Verlag Berlin Heidelberg
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Charnley, S.B. (2011). Molecular Line Cooling. In: Gargaud, M., et al. Encyclopedia of Astrobiology. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-11274-4_1016
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DOI: https://doi.org/10.1007/978-3-642-11274-4_1016
Publisher Name: Springer, Berlin, Heidelberg
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