STRUCTURE OF THE ETHYLENE DIMER FROM ROTATIONALLY RESOLVED NEAR-INFRARED SPECTROSCOPY - A QUADRUPLE HYDROGEN-BOND

Reported here are the first rotationally assigned near-infrared spectra of the ethylene dimer. The vibrational bands observed in this study correlate with ν9 and ν11 of the ethylene monomer, corresponding to C-H stretching motion. The spectral patterns have been identified as due to the vibrational transitions of a symmetric top molecule with D2d symmetry. This structure of the dimer has been predicted by ab initio calculations as the most stable geometry due to the fact that it enables the formation of four equivalent hydrogen bonds. Both vibrational bands show considerable homogeneous broadening corresponding to vibrational predissociation lifetimes of 0.37 and 0.18 ns for ν9 and ν11 excitation, respectively. © 1995 American Institute of Physics.