@article{0067-0049-216-2-30,
  author={Andrew L. Cooksy and C. A. Gottlieb and T. C. Killian and P. Thaddeus and Nimesh A. Patel and Ken H. Young and M. C.
McCarthy},
  title={Vibrationally Excited C4H},
  journal={The Astrophysical Journal Supplement Series},
  volume={216},
  number={2},
  pages={30},
  url={http://stacks.iop.org/0067-0049/216/i=2/a=30},
  year={2015},
  abstract={Rotational spectra in four new excited vibrational levels of the linear carbon chain radical C 4 H were observed in the millimeter band between 69 and 364 GHz in a low pressure glow discharge, and two of these were observed in a supersonic molecular beam between 19 and 38 GHz. All have rotational constants within 0.4% of the ##IMG## [http://ej.iop.org/images/0067-0049/216/2/30/apjs507962ieqn1.gif] {${{X}^{2}}{{{\Sigma }}^{+}}$} ground vibrational state of C 4 H and were assigned to new bending vibrational levels, two each with ##IMG## [http://ej.iop.org/images/0067-0049/216/2/30/apjs507962ieqn2.gif] {$^{2}{\Sigma }$} and ##IMG## [http://ej.iop.org/images/0067-0049/216/2/30/apjs507962ieqn3.gif] {$^{2}{\Pi }$} vibrational symmetry. The new levels are tentatively assigned to the ##IMG## [http://ej.iop.org/images/0067-0049/216/2/30/apjs507962ieqn4.gif] {$1{{\nu }_{6}}$} and ##IMG## [http://ej.iop.org/images/0067-0049/216/2/30/apjs507962ieqn5.gif] {$1{{\nu }_{5}}$} bending vibrational modes (both with ##IMG## [http://ej.iop.org/images/0067-0049/216/2/30/apjs507962ieqn6.gif] {$^{2}{\Pi }$} symmetry), and the ##IMG## [http://ej.iop.org/images/0067-0049/216/2/30/apjs507962ieqn7.gif] {$1{{\nu }_{6}}+1{{\nu }_{7}}$} and ##IMG## [http://ej.iop.org/images/0067-0049/216/2/30/apjs507962ieqn8.gif] {$1{{\nu }_{5}}+1{{\nu }_{6}}$} combination levels ( ##IMG## [http://ej.iop.org/images/0067-0049/216/2/30/apjs507962ieqn9.gif] {$^{2}{\Sigma }$} symmetry) on the basis of the derived spectroscopic constants, relative intensities in our discharge source, and published laser spectroscopic and quantum calculations. Prior spectroscopic constants in the ##IMG## [http://ej.iop.org/images/0067-0049/216/2/30/apjs507962ieqn10.gif] {$1{{\nu }_{7}}$} and ##IMG## [http://ej.iop.org/images/0067-0049/216/2/30/apjs507962ieqn11.gif] {$2{{\nu }_{7}}$} levels were refined. Also presented are interferometric maps of the ground state and the ##IMG## [http://ej.iop.org/images/0067-0049/216/2/30/apjs507962ieqn12.gif] {$1{{\nu }_{7}}$} level obtained with the Submillimeter Array (SMA) near 257 GHz which show that C 4 H is present near the central star in IRC+10216. We found no evidence with the SMA for the new vibrationally excited levels of C 4 H at a peak flux density averaged over a ##IMG## [http://ej.iop.org/images/0067-0049/216/2/30/apjs507962ieqn13.gif] {$3^{\prime\prime} $} synthesized beam of ##IMG## [http://ej.iop.org/images/0067-0049/216/2/30/apjs507962ieqn14.gif] {$\geqslant 0.15$} Jy/beam in the 294–296 and 304–306 GHz range, but it is anticipated that rotational lines in the new levels might be observed in IRC+10216 when ALMA attains its full design capability.}
}