Styrene adsorbs molecularly on a clean Cu (111) surface at 90 K. A stable bilayer structure forms on Cu(111) prior to multilayer formation and the second layer desorbs with a peak temperature ~~15 K higher than that for styrene multilayers. Two-photon photoemission (2PPE) spectroscopy has been used to investigate the interfacial electronic structure, particularly unoccupied electronic states, of styrene adsorbed on Cu(111). The dependence of 2PPE spectra on photon energy establishes the occurrence of photoinduced electron transfer to an unoccupied state at 3.4 eV above the Fermi level (or 1.0 eV below the vacuum level) at 0.7 monolayer coverage. An occupied state located at 1.9 eV below the Fermi level is also observed. Polarization results reveal that the occupied state and the unoccupied state arise from bonding and antibonding orbitals formed by hybridization of copper (surface state and d-band orbitals) and styrene (π₁* and π₂* orbitals).

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