Fourier transform microwave spectroscopic investigation of a very weakly bound ternary complex: OCS–He2

The rotational spectra of the van der Waals complex of carbonyl sulfide loosely bound to two helium atoms were investigated using a cavity Fourier transform microwave spectrometer and a microwave–microwave double resonance spectrometer. The lowest rotational transitions of seven isotopomers, namely those containing the ¹⁶O¹²C³²S, ¹⁶O¹²C³⁴S, ¹⁶O¹³C³²S, ¹⁶O¹²C³³S, ¹⁸O¹³C³²S, ¹⁶O¹³C³⁴S, and ¹⁷O¹³C³²S subunits, were studied. Hyperfine structures due to the quadrupolar ³³S and ¹⁷O nuclei were also observed and analyzed. The search for higher J transitions was not successful and possible causes are discussed. Information about the OCS–He₂ cluster inferred from the measurements is presented and discussed.