The rotational spectrum of the acetylene-carbonyl sulfide trimer: HCCH-(OCS)(2)

The rotational spectrum of the HCCH-OCS-OCS trimer has been assigned. The r otational constants and dipole moment components are consistent with a non- planar, barrel-like structure which aligns the three monomer axes in an alm ost parallel fashion. in this structure, the OCS dimer portion of the trime r has the two OCS molecules aligned in a parallel-like arrangement rather t han the antiparallel geometry found in the OCS dimer. This conformation giv es good agreement with rotational constants and dipole moment components pr edicted from a semi-empirical model and with isotopic shifts observed for t wo other isotopomers. (C) 1999 Elsevier Science B.V. All rights reserved.