MICROWAVE SPECTROSCOPY OF MOLECULAR-COMPLEXES

Weakly bound molecular complexes are formed in supersonic expansions o f seeded rare gases. Their rotational spectra have been observed with pulsed nozzle Fourier transform microwave spectrometers. The analysis of the rotational spectra, usually including isotopic variants of the complexes, has provided valuable information about the geometric struc ture of complexes. When complexes are formed the loss of translational and rotational degrees of freedom of the monomers leads to low-freque ncy Van der Waals vibrations. Often, tunneling motions between equival ent minima of the intermolecular potential energy surface have complic ated the interpretation of the microwave spectra considerably. Centrif ugal distortion and tunnel splittings have given important insights in to the intermolecular dynamics. (C) 1997 Elsevier Science B.V.