The Structure of C2H4 Clusters from Theoretical Interaction Potentials and Vibrational Predissociation Data
Reinhard Ahlrichs, Stefan Brode, Udo Buck, Maarten DeKieviet, Christian Lauenstein, Andreas Rudolph, and Burkhard Schmidt
Optimized geometries and binding energies are calculated for ethene (ethylene) dimers, trimers, and tetramers based on a pairwise additive dimer potential. From these results intermolecular frequencies and relative abundancies (catchment areas) of the different isomers are obtained and compared with the results of accurate measurements of the photodissociation upon absorption of one photon of a CO2 laser in the region of the ν7 monomer absorption band at 949 cm-1. The clusters are size selected in a scattering experiment and show for a cluster size from n=2 to n=6 a frequency maximum shifted by 3 cm-1 to the blue compared with the monomer. The result is explained by the predominance of chains and chain-like structures of the clusters in the photodissociation process. The chains consist of cross-like dimer sub-units.