Isotopic studies of the binary complex He-OCS

Rotational transitions of four isotopologues of the He-OCS van der Waals complex were investigated using a pulsed molecular beam Fourier transform microwave spectrometer, following the original molecular beam electric resonance study of the normal isotopologue of this complex [K. Higgins, W. Klemperer, J. Chem. Phys. 110 (1999) 1383]. This includes 10, 9, and 8 rotational transitions for He-OC34S, He-O13CS, and He-OC33S, respectively, as well as four additional transitions for the normal isotopologue. In the case of the He-OC33S isotopologue, 29 33S nuclear quadrupole hyperfine components were observed and analyzed. The new isotopic data are of importance for the further refinement of the He-OCS potential energy surface.