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The 12C/13C Ratio in Interstellar Dark Clouds

Published online by Cambridge University Press:  14 August 2015

W.H. Mccutcheon ,
R. L. Dickman ,
W.L.H. Shuter  and
R. S. Roger
W.H. Mccutcheon
Affiliation:
University of British Columbia
R. L. Dickman
Affiliation:
Aerospace Corporation
W.L.H. Shuter
Affiliation:
University of British Columbia
R. S. Roger
Affiliation:
Dominion Radio Astrophysical Observatory

Extract

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Since 13C is believed to be produced by non-equilibrium CNO processing in stellar evolution (Truran 1977), measurements of the carbon ratio Rc ≡ [12C] / [13C] in the interstellar medium may provide important information on nucleo-synthesis. Commonly, the ratio (N13/N18)LTE ≡ [13CO/C18O]LTE is measured and from this RLTE ≡ [12CO/13CO]LTE is deduced and these values are often identified with Rc. However, this line of reasoning can be misleading for two reasons (Dickman et al. 1979):

(1) The difficulty of determining accurate column densities, [13C16O] and [12C18O], because of the complexity of the radiative transfer problem;

(2) The possible role of fractionation, whereby RCO ≡ [12CO] / [13CO] does not necessarily reflect the initial atomic abundance ratio RC (Watson et al. 1976, Langer 1977, Liszt 1978).

Type
Research Article
Information
Symposium - International Astronomical Union , Volume 87: Interstellar Molecules , 1980 , pp. 411 - 416
Copyright
Copyright © Reidel 1980 

References

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