...N₂D⁺

Based on observations carried out with the IRAM Pico Veleta telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).

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...

Appendix is only available in electronic form at http://www.aanda.org

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... charged

Although this is probably true within a factor of 2 (e.g. Flower & Pineau des Forêts 2003), this assumption does not affect our conclusions.

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