Infrared spectra of OCS-C6H6, OCS-C6H6-He, and OCS-C6H6-Ne van der Waals complexes

The infrared spectrum of weakly bound OCS\u2013C6H6 is studied in the region of the \u3bd1 fundamental band of OCS ( ~ 2050\u2002cm 121) using a tunable diode laser spectrometer to probe a pulsed supersonic jet expansion. This is one of the first direct infrared observations of a benzene-containing van der Waals complex. A very simple band is observed, corresponding to the parallel transition of a symmetric top. It is shifted by 1211.1\u2002cm 121 with respect to the free OCS monomer. The isotopologues OCS\u201313C\u200912C5H6 and OC\u200934S\u2013C6H6 are observed, and the derived structure has OCS located along the benzene C6 symmetry axis in an S-bonded configuration with a center of mass separation of 4.42 \uc5, in good agreement with previous microwave spectra. Similar bands are observed for the trimers OCS\u2013C6H6\u2013He and OCS\u2013C6H6\u2013Ne, whose structure is obtained by adding an on-axis rare gas atom to the other side of the benzene. However, the analogous band for OCS\u2013C6H6\u2013Ar is not detected, raising the possibility that the stable form of this trimer may not have the same symmetrical structure. A \u201cmystery\u201d feature is observed close to the OCS\u2013C6H6 band origin and its possible assignment to a cluster such as OCS\u2013(C6H6)3 is discussed.Peer reviewed: YesNRC publication: Ye