Detection of the carbon chain negative ion C8H- 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 C4H, have also been determined.