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

Abstract

The cyanopolyyne HC 11 N, 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 ϩ10216 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 HC 11 N to be determined to much better than 1 km s Ϫ1 in equivalent radial velocity. A search for HC 11 N at the correct frequencies in published and unpublished spectra of these sources has turned up no convincing candidate lines, but detection is probably possible with one of the existing large radio telescopes.