Infrared spectra of ethylene clusters: (C2D4)2 and (C2D4)3

Spectra of ethylene dimers and trimers are studied in the \u3bd11 fundamental band region of C2D4 ( 482200 cm 12\ub9) using a tuneable quantum cascade laser to probe a pulsed supersonic slit jet expansion. The dimer spectrum is that of a prolate symmetric top perpendicular band, with a distinctive appearance because the A rotational constant is almost exactly equal to six times the B constant. The analysis supports the previously determined cross-shaped dimer structure with D2d symmetry. An ethylene trimer has not previously been observed with rotational resolution. The spectrum is that of an oblate symmetric top parallel band. It leads to a proposed trimer structure which is barrel shaped and has C3h or C3 symmetry, with the ethylene monomer C\u2013C axes approximately aligned along the trimer symmetry axis.Peer reviewed: YesNRC publication: Ye