INFRARED-LASER JET SPECTROSCOPY OF TRANSITION-METAL HEXACARBONYL-RAREGAS DIMERS

High resolution infrared absorption spectra of nine van der Waals comp lexes M(CO)(6) . Rg (M=Cr, Mo, W; Rg=Ar, Kr, Xe) formed in a supersoni c jet expansion have been recorded near the 5 mu m carbonyl stretching fundamental bands of the hexacarbonyl monomers. In each case a single red-shifted perpendicular band was observed. It is shown that the spe ctral results are only consistent with a C-3 upsilon symmetric top str ucture for each dimer; no effects due to internal motions are seen in the spectra. The M-Rg separations deduced from analysing the spectra a re slightly larger than the separations calculated from the van der Wa als radii. Red-shifts of the band origin are partly explained by a sim ple vibrational dipole-induced dipole model. (C) 1996 American Institu te of Physics.