The Ongoing Saga of Cyanodecapentayne, HC11N, in TMC-1

R. A. Loomis, C. N. Shingledecker, G. Langston, B. A. McGuire, N. M. Dollhopf, A. M. Burkhardt, J. Corby, S. T. Booth, P. B. Carroll, B. Turner, and A. J. Remijan
emphasized the
Non-detection of HC11N towards TMC-1: Constraining the Chemistry of Large Carbon-chain Molecules
Mon. Not. R. Astron. 463, 4175–4183 (2016).
Using the 100 m GBT, the authors have covered six rotational transitions with J" from 37 to 42. No single line was above 2 σ, and the stacked recordings yield an unsignificant result at the 2 σ level. Using the data from Bell at al., 1997 (see next paragraph), they should have observed most lines at about the 3 σ level, and even more clearly in the stacked observations. They conclude from the latter a 3 σ upper limit of about 1011 cm–2.

M. B. Bell, P. A. Feldman, M. J. Travers, M. C. McCarthy, C. A. Gottlieb, and P. Thaddeus
reported on the
Detection of HC11N in the Cold Dust Cloud TMC-1
Astrophys. J. 483, L61–L64 (1997).
Two transitions, J = 39 – 38 and 39 – 38 near 12.849 and 13.187 GHz were identified with the 43 m Green Bank Telescope. The invoked column density is 2.8 × 1011 cm–2 for a temperature of 10 K.
An earlier report was in error. The erroneous assignments were based on an extrapolation of the rotational constant B by
T. Oka,
The Prediction of the Rotational Constants of Polyacetylene Compounds H–(C≡C)n–C≡N
J. Mol. Spectrosc. 72, 172–174 (1978);
which in the end turned out to be in full agreement with the laboratory data and thus to be much better than implied by the earlier purported astronomical identification.

Contributor(s): H. S. P. Müller; 02, 2006; 10, 2008; 11, 2016