THE ROTATIONAL SPECTRUM OF THE CARBON CHAIN RADICAL HCCCO

The bent chain radical HCCCO has been identified from laboratory measurement of 248 rotational transitions between 81 and 400 GHz. Because two molecules with the same heavy atom backbone, CCCO and HCCCHO, have already been observed in TMC-1, HCCCO is a good candidate for detection in molecular clouds and circumstellar envelopes. Rotational transition frequencies for the K(a)= 0 manifold are tabulated, as well as precise values for the rotational, centrifugal distortion, and spin-rotation constants, which allow calculation of the entire rotational spectrum into the far-IR.