D. T. HALFEN, Steward Observatory, University of Arizona, Tucson, AZ, 85721; D. J. CLOUTHIER, Department of Chemistry, University of Kentucky, Lexington, KY, 40506; AND L. M. ZIURYS, Department of Chemistry, Department of Astronomy, and Steward Observatory, University of Arizona, Tucson, AZ, 85721.
The CCP radical (X2 r) has been detected in the circumstellar gas of IRC+10216, the fifth phosphorus-bearing molecule identified in interstellar space. Four rotational transitions of this species were observed using the Arizona Radio Observatory (ARO) 12m telescope on Kitt Peak at 2 and 3 mm. Each transition consists of lambda-doublets, which are well-separated in frequency in IRC+10216; five of these eight possible lines of CCP were clearly detected, while the remaining three were contaminated by stronger emission from other species. The column density derived for CCP was Ntot = 1x1012 cm-2 and Trot = 21 K. Modeling of the line profiles suggests that CCP arises from an extended shell with a maximum radius of 40". The abundance of this radical, relative to H2, is f = 1x10-9 - roughly comparable to that of PN and CP in this source. CCP may be produced from radical-radical reactions of CP, or ion-molecule chemistry involving P+ and HCCH. The identification of CCP is additional evidence that phosphorus chemistry is active in carbon-rich circumstellar gas.