			15min:

INFRARED SPECTRA AND AB INITIO POTENTIAL ENERGY SURFACES FOR ACETYLENE COMPLEXED TO Mg ATOMS AND CLUSTERS.

DAVID T. MOORE, ROGER E. MILLER, Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599.

We have recently developed a technique to measure high-resolution infrared spectra of molecules attached to metal atoms and clusters. Using this technique, the spectrum of the CH stretching band of the acetylene-Mg van der Waals complex has been measured in superfluid liquid ⁴He droplets. A pure b-type band was observed, indicating that the vibrationally averaged structure of the complex is T-shaped, with the Mg atom binding to the -cloud of the acetylene. Spectral bands corresponding to acetylene-Mg_n (n=2-4) complexes were also observed. Structural interpretations based on these spectra will be discussed. High level [CCSD(T)/6-311++G(3df,3pd)] ab initio potential energy surfaces were also constructed for these complexes, and structural predictions based on these calculations will be compared with the experimentally determined structures.