Intermolecular dynamics of benzene–rare gas complexes as derived from microwave spectra

Abstract

The rotational spectra of three benzene–X complexes, where X=20Ne, 129Xe, or 132Xe, and of the benzene-1,3,5-d3–Ar complex have been observed using pulsed nozzle Fourier transform microwave (FTMW) spectroscopy. Rotational transitions assigned in the 8–18 GHz range have been found to match symmetric top spectra. Rotational constants B and centrifugal constants DJ and DJK were determined from the measured frequencies. Intermolecular motions between benzene and the rare gas atom have been modeled with a rovibrational Hamiltonian. The three-dimensional interaction potential has been assumed of a simple form with three adjustable parameters. These parameters, one of which represents the equilibrium distance of the rare gas atom from the plane of benzene, have been adjusted for all benzene–rare gas complexes in a least-squares fit by direct inversion of the observed rotational transition frequencies. From the potential, the force constants and frequencies of the van der Waals vibrations and the binding energies have been deduced for all benzene–rare gas complexes.