... regions[*]
Appendices are only available in electronic form at http://www.aanda.org
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... only[*]
We neglect line overlap.
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... 1[*]
Because $\frac{A_{21}}{k_{21}~ n}\;
\exp\left( \frac{T_{12}}{T_{\rm k}}\right)>1$.
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Copyright ESO 2008