@article{2041-8205-843-2-L28,
  author={Brett A. McGuire and Andrew M. Burkhardt and Christopher N. Shingledecker and Sergei V. Kalenskii and Eric
Herbst and Anthony J. Remijan and Michael C. McCarthy},
  title={Detection of Interstellar HC 5 O in TMC-1 with the Green Bank Telescope},
  journal={The Astrophysical Journal Letters},
  volume={843},
  number={2},
  pages={L28},
  url={http://stacks.iop.org/2041-8205/843/i=2/a=L28},
  year={2017},
  abstract={We report the detection of the carbon-chain radical HC 5 O for the first time in the interstellar medium toward the cold core TMC-1 using the 100 m Green Bank Telescope. We observe four hyperfine components of this radical in the ##IMG## [http://ej.iop.org/images/2041-8205/843/2/L28/apjlaa7ca3ieqn1.gif] {$J=17/2\to 15/2$} rotational transition that originates from the ##IMG## [http://ej.iop.org/images/2041-8205/843/2/L28/apjlaa7ca3ieqn2.gif] {${}^{2}{{\rm{\Pi }}}_{1/2}$} fine structure level of its ground state and calculate an abundance of ##IMG## [http://ej.iop.org/images/2041-8205/843/2/L28/apjlaa7ca3ieqn3.gif] {$n/{n}_{{H}_{2}}=1.7\times {10}^{-10}$} , assuming an excitation temperature of ##IMG## [http://ej.iop.org/images/2041-8205/843/2/L28/apjlaa7ca3ieqn4.gif] {${T}_{\mathrm{ex}}=7$} K. No indication of HC 3 O, HC 4 O, or HC 6 O, is found in these or archival observations of the source, while we report tentative evidence for HC 7 O. We compare calculated upper limits and the abundance of HC 5 O to predictions based on (1) the abundance trend of the analogous HC n N family in TMC-1 and (2) a gas-grain chemical model. We find that the gas-grain chemical model well reproduces the observed abundance of HC 5 O, as well as the upper limits of HC 3 O, HC 6 O, and HC 7 O, but HC 4 O is overproduced. The prospects for astronomical detection of both shorter and longer HC n O chains are discussed.}
}