First Observation And Analysis Of Ocs−c4h2 Dimer And (ocs)2−c4h2 Trimer

Infrared spectrum of a slipped near parallel isomer of \chem{OCS-C_4H_2} was observed in the region of \nub{1} fundamental band of \chem{OCS} monomer ($\mathtt{\sim}$2062 \wn) using a diode laser to probe the supersonic slit jet expansion. The \textit{ab initio} calculations at MP2 level indicate that the observed structure is the lowest energy isomer. The \chem{OCS-C_4H_2} band is composed of hybrid a/b-type transitions and was simulated by a conventional asymmetric top Hamiltonian with rotational constants of A=2892.15(10) MHz, B=1244.178(84) MHz, and C=868.692(52) MHz. The spectrum shows a relatively large red-shift of~$\mathtt{\sim}$6~\wn with respect to the \chem{OCS} monomer band origin. Also, one band for \chem{(OCS)_2-C_4H_2} trimer is observed around 2065 \wn. This band is blue-shifted by 3 \wn relative to the \nub{1} fundamental band of \chem{OCS} monomer. Our analysis shows that this trimer has \textit{C}$_{2}$ symmetry with rotational constants of A= 855.854(61) MHz, B=733.15(11) MHz, and C=610.10(38)~MHz and c-type transitions. This structure is comparable with that of \chem{(OCS)_2-C_2H_2} where the \chem{OCS} dimer unit within the trimer is non-polar.\footnote{Mojtaba Rezaei, A. R. W. McKellar, and N. Moazzen-Ahmadi, J. Phys. Chem. A, \textbf{115}, 10416 (2011).} In addition to the normal isotoplogues, \chem{OCS-C_4D_2} and \chem{(OCS)_2-C_4D_2} were observed. In this talk, we discuss our observations and analysis on \chem{OCS-C_4H_2} dimer and \chem{(OCS)_2-C_4H_2} trimer