15min:
INFRARED SPECTRA OF CARBONYL SULFIDE-ACETYLENE TRIMERS: OCS-(C2H2)2 AND TWO ISOMERS OF (OCS)2-C2H2.

MAHIN AFSHARI, M. DEHGHANY, J. N. OLIAEE, N. MOAZZEN-AHMADI, Department of Physics and Astronomy, University of Calgary, Calgary, AB T2N 1N4, Canada; A. R. W. MCKELLAR, Steacie Institute for Molecular Sciences, National Research Council of Canada, Ottawa, ON K1A 0R6, Canada.

Spectra of acetylene-carbonyl sulphide trimers in the region of the OCS nu1 fundamental ( sim2062 cm-1) are observed using a tunable diode laser to probe a pulsed supersonic slit jet expansion. A previous microwave study of (OCS)2- C2H2 by Peebles and Kuczkowski gave a nonplanar triangular twisted structure, which could be thought of as a polar OCS dimer plus a C2H2 monomer lying above the dimer plane. In the present work, three infrared bands are analyzed. The first band clearly belongs to this previously known (OCS)2-C2H2 complex. The second band can be assigned as an isomer of (OCS)2-C2H2 having a similar structure, but with a nonpolar OCS dimer plus a C2H2 monomer above the dimer plane. The third band is assigned to OCS-(C2H2)2. The rotational constants and dipole moment components of all three bands are consistent with barrel shape structures having C1, C2 and Cs symmetries, respectively.