Laboratory detection and astronomical identification of a new free radical, CCS 3Sigma/-/

The linear CCS radical has been detected, for the first time, by laboratory microwave spectroscopy, and four unidentified lines including the U45379 line from TMC-1 and seven from Sgr B2 have been assigned to the transitions of this radical. The radical was produced in a free-space absorption cell by a dc glow discharge in a mixture of CS2 and He. Twenty-nine lines were observed in the frequency region up to 300 HGz and were least-squares analyzed to determine the detailed molecular constants. Two strong unidentified lines, U45379 and U22344, were assigned to the F1 components, J(N) = 4(3)-3(2) and 2(1)-1(0), respectively. The J(N) = 2(1)-1(0) transition of CC(S-34) was also observed in TMC-1. The column densities of CCS in Sgr B2 and TMC-1 are estimated to be (6 + or - 1) x 10 to the 13th and (8 + or - 2) x 10 to the 13th per sq cm, respectively.