STRUCTURE OF THE FLUORENE BENZENE AROMATIC DIMER FROM ROTATIONAL COHERENCE SPECTROSCOPY

Rotational coherence spectroscopy has been used to measure rotational constants for four isotopomers of the aromatic-aromatic dimer fluorene-benzene. Possibilities for the vibrationally averaged dimer geometry have been deduced from the measured values. In the geometries the benzene moiety is above the five-membered ring of fluorene, displaced away from the apex of that ring, and tilted into the plane of the fluorene. The geometries are discussed in terms of the intermolecular forces between the species and the theoretical and experimental results on other aromatic dimer structures.