Electron Dynamics at Polyacene/Au(111) Interfaces

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• 作者：C. D. Lindstrom ; M. Muntwiler ; X.-Y. Zhu
• 刊名：Journal of Physical Chemistry B
• 出版年：2007
• 出版时间：June 21, 2007
• 年：2007
• 卷：111
• 期：24
• 页码：6913 - 6920
• 全文大小：282K
• 年卷期：v.111,no.24(June 21, 2007)
• ISSN：1520-5207

文摘

Two-photon photoemission (2PPE) spectroscopy is used to examine the excited electronic structure anddynamics at polyacene/Au(111) interfaces. Image resonances are observed in all cases (benzene, naphthalene,anthrathene, tetracene, and pentacene), as evidenced by the free-electron like dispersions in the surface planeand the dependences of these resonances on the adsorption of nonane overlayers. The binding energies andlifetimes of these resonances are similar for the five interfaces. Adsorption of nonane on top of these filmspushes the electron density in the image resonance away from the metal surface, resulting in a decrease in thebinding energy (-0.3 eV) and an increase in the lifetime (from <20 to ~110 fs). The insensitivity of theimage resonances to the size of polyacene molecules and the absence of photoinduced electron transfer fromthe metal substrate to molecular states both suggest that the unoccupied molecular orbitals are not stronglycoupled to the delocalized metal states or image potential resonances.