Detection of the Carbon Chain Negative Ion C 8 H - in TMC-1

The negative molecular ion C 8 H - has been detected in the Galactic molecular source TMC-1. Four rotational transitions have been observed in the centimeter-wave band with the NRAO 100 m Green Bank Telescope (GBT) at precisely the frequencies calculated from the recent laboratory spectroscopy of this large carbon chain anion. C 8 H - is about 5% as abundant as C 8 H, or somewhat more than C 6 H - relative to C 6 H (1.6%). Improved values of the column densities of C 6 H - and C 6 H, and an upper limit for the abundance of the smaller carbon chain C 4 H - of 0.014% with respect to C 4 H, have also been determined.