Millimeter-wave spectrum of the CCO radical

The pure rotational spectrum of the CCO radical in the /sup 3/..sigma../sup -/ ground electronic state has been observed in the laboratory in the region 45-185 GHz. The radical was generated in a 3.5 m long free space absorption cell by a DC glow discharge in carbon suboxide (C/sub 3/O/sub 2/). Seven rotational transitions of Nn = 2reverse arrow1 to 8reverse arrow7 in each triplet sublevels were precisely measured and the observed frequencies were least-squares analyzed to obtain molecular constants.