, 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 
,
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 C
H. For the 
lines, the center of the
two doublets is contaminated by c-C
H, but MgCN emission is
distinctly present.