The normal isotopomer and three additional isotopic species of the OCS-(HCC
H)(2) trimer have been observed by pulsed nozzle Fourier transform microwav
e spectroscopy. Semi-empirical modeling predicts a structure that has the t
wo acetylene monomers aligned in a geometry between the well-known T-shaped
orientation of the acetylene dimer and a parallel intermediate. Rotational
constants and dipole moment measurements are consistent with this model. (
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