Rotational Spectroscopy of PAHs: Acenaphthene, Acenaphthylene and   Fluorene
  Pure rotational spectra of three polycyclic aromatic hydrocarbons - acenaphthene, acenaphthylene and fluorene - have been obtained by Fourier transform microwave spectroscopy of a molecular beam and subsequently by millimeter wave absorption spectroscopy for acenaphthene and fluorene. The data presented here will be useful for deep radio astronomical searches for PAHs employing large radio telecopes. 
S. Thorwirth, P. Theule, C. A. Gottlieb, M. C. McCarthy and P.   Thaddeus