H
, J. Cernicharo 
, M.J. Travers
, M.C. McCarthy , C.A. Gottlieb , P. Thaddeus
, M. Ohishi 
, S. Saito 
,
S. Yamamoto 
IRAM, 300 Rue de la piscine, F-38406 S 
Martin
d'Hères, France Observatorio Astronomico Nacional,
apartado 1143, E-28800 Alcalá de Henares, Spain Division of Applied Sciences, Harvard University,
Cambridge, MA 02138, USA N. R. O., Minamimaki, Minamisaku, Nagano 384-13, Japan Institute for Molecular Science, Myodaiji, Okazaki 444, Japan Dept. of Physics, The University of Tokyo, Bunkyo-ku, Tokyo 113, Japan 
H in IRC+10216 (Cernicharo & Guélin 1996), we
report the detection in this circumstellar envelope of another linear
carbon chain radical, C H. The microwave spectrum of
C H has been recently observed in the laboratory and its rotational line
frequencies are precisely known.
With this new detection, the family of acetylenic chain radicals (C 
H)
observed in space is complete up to n= 8. The members with even numbers of
carbon atoms are consistently more abundant than the odd number members;
C H is found to be a factor of 4 less abundant than C H and a factor
of 20 less abundant than C 
H.
Figure 1: Four 30-m telescope spectra covering 4 rotational transitions of
C H (the 
doublet components are indicated by vertical arrows).
Two 8 MHz-wide intervals contaminated by strong lines from the upper sideband
have been deleted. Unidentified lines are denoted `U'.
Note the N= 7-6 doublet of vibrationally excited MgNC and the possible
identification of H 
C 
at 83264 MHz, on the right side of the C H
line.