THE ETHYLENE CARBON-DIOXIDE COMPLEX - A DOUBLE INTERNAL ROTOR

A rotationally resolved near-infrared spectrum has been obtained for t he ethylene-CO2 van der Waals complex. The structure obtained for this complex has the carbon dioxide lying above the plane of the ethylene molecule, with the CO2 axis parallel to this plane. The individual sub bands observed in the spectrum are shifted from the expected rigid rot or positions, indicative of internal rotation of the two monomer units within the complex. A double rotor model is presented that accounts f or the shifts and provides an estimate of the barrier to internal rota tion. The results indicate that the complex is completely delocalized along the internal rotational coordinate. Ab initio calculations are a lso presented that are in good agreement with this picture. (C) 1995 A merican Institute of Physics.