Laboratory Detection of the Linear Cyanopolyyne HC[TINF]11[/TINF]N

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Abstract
The cyanopolyyne HC11N, the largest claimed interstellar molecule, has been detected in the laboratory. Its nearest microwave rotational transitions lie 0.13% lower in frequency than the lines identified in IRC +10216 and TMC-1, so it is concluded that the astronomical lines are something else entirely. The 20 laboratory lines measured with our Fourier transform molecular-beam spectrometer allow the entire microwave spectrum of HC11N to be determined to much better than 1 km s-1 in equivalent radial velocity. A search for HC11N at the correct frequencies in published and unpublished spectra of these sources has turned up no convincing candidate lines, but detection is probably possible with one of the existing large radio telescopes.