Electronic structure and excited state dynamics in optically excited PTCDA films investigated with two-photon photoemission
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Output type: Journal article
Author list: Marks M., Sachs S., Schwalb C., Schöll A., Höfer U.
Publisher: American Institute of Physics
Publication year: 2013
Journal: The Journal of Chemical Physics (0021-9606)
Volume number: 139
Issue number: 12
Number of pages: 8
ISSN: 0021-9606
eISSN: 1089-7690
URL: http://api.elsevier.com/content/abstract/scopus_id:84885465097
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Open access status: closed
Abstract
We present an investigation of the electronic structure and excited state dynamics of optically excited 3,4,9,10-perylene-tetracarboxylic acid dianhydride (PTCDA) thin films adsorbed on Ag(111) using two-photon photoemission spectroscopy (2PPE). 2PPE allows us to study both occupied and unoccupied electronic states, and we are able to identify signals from the highest occupied and the two lowest unoccupied electronic states of the PTCDA thin film in the 2PPE spectra. The energies for occupied states are identical to values from ultraviolet photoelectron spectroscopy. Compared to results from inverse photoelectron spectroscopy (IPES), the 2PPE signals from the two lowest unoccupied electronic states, LUMO and LUMO+1, are found at 0.8 eV and 1.0 eV lower energies, respectively. We attribute this deviation to the different final states probed in 2PPE and IPES and the attractive interaction of the photoexcited electron and the remaining hole. Furthermore, we present a time-resolved investigation of the excited state dynamics of the PTCDA film in the femtosecond time regime. We observe a significantly shorter inelastic excited state lifetime compared to findings from time-resolved photoluminescence spectroscopy of PTCDA single crystals which could originate from excitation quenching by the metal substrate. © 2013 AIP Publishing LLC.
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