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Title: DETECTION OF CCN (X {sup 2}Π{sub r}) IN IRC+10216: CONSTRAINING CARBON-CHAIN CHEMISTRY

The CCN radical (X {sup 2}Π{sub r}) has been detected for the first time in the interstellar medium. The molecule was observed at the 1-2 mK level toward the circumstellar envelope of IRC+10216, using the facilities of the Arizona Radio Observatory (ARO). Lambda doublets of the J = 4.5 → 3.5 and the J = 6.5 → 5.5 transitions at 106 GHz and 154 GHz in the Ω = 1/2 ladder were measured with the ARO 12 m telescope, as well as the J = 9.5 → 8.5 lines near 225 GHz, using the ARO Sub-Millimeter Telescope (SMT). In the two lower frequency transitions, the e component of the doublet was partially blended with other lines, while emission from the f component was uncontaminated. The lambda doublet of the 1 mm transition is collapsed and appears adjacent to an unidentified line. Modeling of the spectra, using the new radiative transfer code ESCAPADE, indicates that CCN arises from a shell in the outer envelope centered at r ∼ 3 × 10{sup 16} cm, with a peak fractional abundance of f {sub 0} ∼ 6 × 10{sup –8}. The column density of the radical is ∼4 × 10{sup 13} cm{sup –2}, in agreement with that derived frommore » a rotational diagram analysis. Modeling was also conducted for spectra of CN, C{sub 3}N, and HC{sub 3}N, obtained with the SMT in the ARO 1 mm survey. CCN, C{sub 3}N, and HC{sub 3}N appear to originate from adjacent shells in the envelope, suggesting they are chemically related. The [CN]/[CCN]/[C{sub 3}N] abundance ratio was found to be ∼500:1:50.« less
Authors:
;  [1]
  1. Department of Chemistry, University of Arizona, PO Box 210041, Tucson, AZ 85721 (United States)
Publication Date:
OSTI Identifier:
22364921
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 795; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CARBON NITRIDES; COMPUTERIZED SIMULATION; DETECTION; DIAGRAMS; GHZ RANGE; INTERSTELLAR SPACE; MOLECULES; NITRILES; RADIANT HEAT TRANSFER; RADICALS; STARS; TELESCOPES