@article{0067-0049-217-1-10,
  author={Michael C. McCarthy and Kyle N. Crabtree and Marie-Aline Martin-Drumel and Oscar Martinez Jr. and Brett A.
McGuire and Carl A. Gottlieb},
  title={A Laboratory Study of C3H+ and the C3H Radical in Three New Vibrationally Excited 2Σ States Using a Pin-Hole Nozzle Discharge Source},
  journal={The Astrophysical Journal Supplement Series},
  volume={217},
  number={1},
  pages={10},
  url={http://stacks.iop.org/0067-0049/217/i=1/a=10},
  year={2015},
  abstract={Rotational lines of the positive molecular ion C 3 H + and of the neutral C 3 H radical in three new vibrationally excited states with 2 Σ symmetry have been detected in a supersonic molecular beam in the centimeter-wave band. The fundamental rotational line of the ion is quite weak, but is observed with similar intensity in a dc discharge through several different hydrocarbon gases when helium is the buffer gas. Under these conditions, the fractional abundance of C 3 H + relative to C 3 H is estimated to be of order 10 −4 , i.e., toward the lower end of the ratio (10 −3 –10 −4 ) found for protonated ions using the same discharge nozzle. For each new 2 Σ state of the C 3 H radical, spectroscopic constants, including those describing hydrogen hyperfine structure, have been determined to high precision. Lines of one 2 Σ state ( B = 11271 MHz) are particularly intense in our molecular beam; for this state and a second one ( B = 11306 MHz), millimeter-wave transitions have also been observed between 180 and 340 GHz using a long path dc glow absorption spectrometer. On the basis of intensity measurements with this spectrometer, the inferred rotation–vibration constant α , and theoretical calculations, the state with B = 11271 MHz is tentatively assigned to the ν 5 bending mode, predicted to lie ∼300 cm −1 above ground.}
}