Darmstadt 2008 – scientific programme
Parts | Days | Selection | Search | Downloads | Help
MO: Fachverband Molekülphysik
MO 14: Cluster
MO 14.3: Talk
Thursday, March 13, 2008, 09:00–09:15, 3G
What microwave spetroscopy tells us about the benzene dimer — •Undine Erlekam1, Melanie Schnell1, Gerard Meijer1, Gert von Helden1, Jens-Uwe Grabow2, and Philip R. Bunker3 — 1Fritz-Haber-Institut der MPG, Berlin, Germany — 2Institut für Physikalische Chemie, Leibniz-Universität, Hannover, Germany — 3Steacie Institute for Molecular Sciences, NRC, Ottawa, Canada
The benzene dimer is a model system for investigating dispersive intermolecular interactions between aromatic molecules. Numerous theoretical and experimental studies exist. Infrared and Raman spectra show different signatures for the two benzene rings in the dimer from which it can be concluded that they are symmetrically inequivalent. Different theoretical calculations find two different minimum structures for the benzene dimer. One is a “parallel-displaced” structure, and the other a distorted T-shaped one with “stem” and “top” benzene rings. The former structure has symmetrically equivalent rings, whereas the latter has symmetrically inequivalent rings in agreement with the Infrared and Raman studies.
We try to solve this conflict using microwave spectroscopy in the 3 to 6 GHz range. In agreement with the only previous microwave study we find a group of microwave transitions, which fit a symmetric top Hamiltonian. It consists of a quartet fine structure with a characteristic intensity and splitting pattern. To explore the origin of this splitting we have studied the microwave spectrum of the (C6H6)2 and C6H6-C6D6 isotopologs. Our experimental results will be presented and discussed in the light of the nuclear spin statistics.