AVS 47th International Symposium
    Surface Science Wednesday Sessions
       Session SS1-WeM

Paper SS1-WeM7
Direct Experimental Measurement of Donation/Backdonation in Unsaturated Hydrocarbons Bonding to Metals

Wednesday, October 4, 2000, 10:20 am, Room 208

Session: Chemical Interactions and Surface Reactivity
Presenter: L. Triguero, Uppsala University, Sweden
Authors: L. Triguero, Uppsala University, Sweden
A. Föhlisch, Universität Hamburg, Germany
P. Väterline, Uppsala University, Sweden
J. Hasselström, Uppsala University, Sweden
M. Weinelt, Universität Erlangen, Germany
L.G.M. Pettersson, Stockholm University, Sweden
A. Nilsson, Uppsala University, Sweden
Correspondent: Click to Email
Soft X-ray emission spectra (XES) from C@sub 2@H@sub 4@/Cu(110) and C@sub6@H@sub6@/Cu(110) have been obtained for two excitation energies, resonant and non-resonant, and resolved in all three spatial components (x, y, z). The one-step theory for resonant soft X-ray spectroscopy and Raman scattering is extended to adsorbates on metal surfaces and is implemented within a density functional theory framework. A combination of these expermiental and theoretical works are used to examine the electronic structure of chemisorbed ethylene and benzene on the Cu(110) surface in order to investigate the suitability of the donation/backdonation bonding model given by Dewar, Chatt and Duncanson for the interaction of unsaturated hydrocarbons with metal surfaces. We give an experimental verification of the DCD model and find donation/backdonation to be twice as large for ethylene as for benzene. In particular, the degree of @sigma@--@pi@ mixing (rehybridization) is found to correspond to the amount of donation/backdonation, which is put into relation to the aromatic and non-aromatic @pi@ characters of benzene and ethylene, respectively.