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Detection of MgCN in IRC+10216 : A New Metal-bearing Free Radical

L.M. Ziurys , A.J. Apponi , M. Guélin , J. Cernicharo
Department of Chemistry, Arozona State University, Tempe, AZ 85287-1604, USA
IRAM, 300 rue de la Piscine, 38406 St. Martin d'Hères, France
Centro Astronómico de Yebes, I.G.N., 19080 Guadalajara, Spain
Abstract: A new metal-containing molecule, MgCN, has been detected towards the late-type star IRC+10216, using the NRAO 12m and IRAM 30m telescopes (Fig. 3). The , and transitions of this species, which has a ground state, have been observed in the outer envelope of this objects at 3mm. For the transition, the two spin-rotation components are clearly resolved and conclusively identify this new radical. These measurements imply a column density for MgCN of cm in the outer shell, which corresponds to a fractional abundance of . This molecule, the metastable isomer of MgNC, is the third metal-bearing species thus far identified in the outer shell of IRC+10216, and its detection implies a ratio of MgNC/MgCN . MgCN may be formed through a reaction scheme involving magnesium and HNC or CN, both prominent outer shell molecules, or through synthesis or grains.

Figure 3: Spectrum of the , , and transitions of MgCN obtained with the IRAM 30m telescope towards IRC+10216 at 112, 102, and 92 GHz, using 1 MHz resolution. Assumed LSR velocity is -26.4 km/s. The spin-doublets are clearly resolved in these data (see the expected doublet profile drawn below the spectrum in dotted line). Again, one doublet of the transition is partially obscured by CH. For the lines, the center of the two doublets is contaminated by c-CH, but MgCN emission is distinctly present.

Robert Lucas
Fri Mar 17 14:32:02 MET 1995