2007A&A...464L..33B

This paper reports the laboratory detection of the rotational spectrum of the acetylide anion, CCH^–. Five successive rotational transitions have been measured to high accuracy in a dc discharge with a free space millimeter-wave spectrometer in the frequency range 83-417GHz. Precise spectroscopic constants have been obtained for CCH^– and transition rest frequencies can now be calculated to better than 1km/s in equivalent radial velocity far into the terahertz region, allowing for deep astronomical searches for this anion in space. The highly stable and fairly polar CCH^– anion is a likely candidate for radio astronomical detection, its neutral analogue CCH being among one of the most abundant molecules in a wide variety of astrophysical sources.