@article{0004-637X-662-2-1309,
  author={S. Thorwirth and P. Theulé and C. A. Gottlieb and M. C. McCarthy and P. Thaddeus},
  title={Rotational Spectra of Small PAHs: Acenaphthene, Acenaphthylene, Azulene, and Fluorene},
  journal={The Astrophysical Journal},
  volume={662},
  number={2},
  pages={1309},
  url={http://stacks.iop.org/0004-637X/662/i=2/a=1309},
  year={2007},
  abstract={Pure rotational spectra of four small polycyclic aromatic hydrocarbons have been observed by Fourier transform microwave spectroscopy of a molecular beam in the frequency range from 7 to 37 GHz. Initial searches for acenaphthene (C 12 H 10 ), acenaphthylene (C 12 H 8 ), and fluorene (C 13 H 10 ) were guided by quantum chemical calculations performed at the B3LYP/cc-pVTZ level of theory. All three molecules exhibit b -type rotational spectra and are calculated to be moderately polar, with dipole moments of 0.3-0.9 D. Close agreement (to better than 1%) between the calculated equilibrium and experimentally derived ground-state rotational constants is achieved. Selected transitions of acenaphthene and fluorene have also been measured in the 3 mm region by conventional free-space absorption spectroscopy, as have transitions of the previously studied azulene (C 10 H 8 ). The data presented here facilitate deep radio astronomical searches with large radio telescopes.}
}