Tentative detection of the C/sub 3/N radical

A new molecule, probably the cyanoethynyl radical C/sub 3/N, has been discovered in the molecular envelope of IRC+10216. The identification is based on the detection of two nearly identical emission-line doublets split by 18.7 MHz, one centered at 89055 MHz, the other at 98949 MHz. These are the J=9..-->..8 and 10..-->..9 rotational transitions of C/sub 3/N; the electronic ground state of this radical is /sup 2/..sigma.., and the doublet structure in the rotational transitions is spin-doubling by the single unpaired electron. The rotation, centrifugal distortion, and spin-doubling constants of C/sub 3/N derived from the astronomical data are B/sub 0/=4947.66 +- 0.15 MHz, D/sub 0/=1 +- 1 kHz, and vertical-bar..gamma..vertical-bar=18.7 +- 0.5 MHz.