Accurate spectroscopy of polycyclic aromatic compounds: From the rotational spectrum of fluoren-9-one in the millimeter wave region to its infrared spectrum

The rotational spectrum of fluoren-9-one, a small oxygenated polycyclic aromatic hydrocarbon, has been recorded and assigned in the 52-74.4 GHz region. The determined small negative value of the inertia defect (−0.3 uA^2) has been explained in terms of vibrational-rotational coupl-ing constants alculated at the B3LYP/cc-pVTZ level of theory. Vibrational anharmonic anal-ysis together with second-order vibrational perturbation theory pproximation was applied bothto fluorenone and its reduced form, fluorene, o predict the mid- and near-infrared spectra. The data presented here give recise indication on the fluorenone ground state structure, allow for anaccurate spectral characterization in the millimeter wave and infrared regions, and hopefully willfacilitate extensive radio astronomical searches with large radio telescopes