Berlin 2015 – scientific programme
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O: Fachverband Oberflächenphysik
O 41: Inorganic/Organic Interfaces
O 41.8: Poster
Tuesday, March 17, 2015, 18:15–21:00, Poster B
Femtosecond time-resolved two-photon photoemission spectroscopy of C6H5X/D2O/Cu(111) — •Ishita Agarwal, Isabella Avigo, Samad Abdul Sayed, Manual Ligges, Vesna Mikšić Trontl, Ping Zhou, and Uwe Bovensiepen — University of Duisburg-Essen, Duisburg, Germany
The electron dynamics at a metal-molecule interface is studied with time-resolved two-photon photoemission. We report here energies, workfunction changes and lifetimes of excited electronic states in amorphous D2O/Cu(111) and coadsorbed C6H5F systems after optical excitation with 3.8 eV + 1.9 eV femtosecond laser pulses. We observe a decrease in lifetime of the solvated electron state from 90±5 fs for bare D2O to 60±5 fs for coadsorbed C6H5F. Further, after a total estimated exposure to 0.5×106 photons per C6H5F molecule, a workfunction change of 200±50 meV was observed. Due to the absence of photo-induced workfunction changes in the single stack D2O/Cu(111) and C6H5F/Cu(111), this change is concluded to be mediated by solvated electrons. Additional experiments on C6H5Cl/D2O/Cu(111) were performed and an even larger photoinduced workfunction change was observed. The increase in workfunction is explained by the formation of F−/Cl− as a photo-chemical dissociation product [1,2]. We conclude to have identified the charge transfer to C6H5F(/Cl) and a fingerprint of its photoinduced dissociation. Future experiments aim to systematically change the UV photon energy and the molecule acceptor level.
S. Ryu, et al., J. Am. Chem. Soc., 128, 3500 (2006)
M. Bertin, et al., Faraday Discuss., 141, 293, (2009)