A search for interstellar ch3d: limits to the methane abundance in orion-kl

Maria Womack, A. J. Apponi, L. M. Ziurys

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12 Scopus citations


A search has been performed for interstellar CH3D via its JK = 10-00 transition at 232 GHz and its JK = 20-10 and JK = 21-11 lines at 465 GHz using the NRAO 12 m and CSO 10 m telescopes toward Orion-KL. This search was done in conjunction with laboratory measurements of all three transitions of CH3D using millimeter/submillimeter direct absorption spectroscopy. The molecule was not detected down to a 3 σ level of TA< 0.05 K for the JK = 21-11 line toward Orion, which indicates an upper limit to the CH3D column density of N < 6 × 1018 cm-2 in the hot core region and a fractional abundance (with respect to H2) of <6 × 10-6. These measurements suggest that the methane abundance in the Orion hot core is f < 6 × 10-4, assuming D/H ∼ 0.01. Such findings are in agreement with recent hot core chemical models, which predict CH4/H2 ∼ 10-4.

Original languageEnglish (US)
Pages (from-to)897-901
Number of pages5
JournalAstrophysical Journal
Issue number2 PART I
StatePublished - 1996


  • Ism: Abundances
  • Ism: Clouds
  • Ism: Individual (orion-kl)
  • Ism: Molecules
  • Molecular processes

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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