Berlin 2005 – wissenschaftliches Programm
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O: Oberflächenphysik
O 5: Zeitaufgelöste Spektroskopie I
O 5.9: Vortrag
Freitag, 4. März 2005, 12:45–13:00, TU EB107
Dynamics of Electron Transfer, Trapping, and Solvation in D2O/Ru(001) — •Julia Stähler, Uwe Bovensiepen, Cornelius Gahl, and Martin Wolf — Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
The dynamics of excess electrons photo-injected into ultrathin ice layers on Ru(001) has been studied by femtosecond time-resolved two photon photoelectron (2PPE) spectroscopy. The electrons’ residence time in the adlayer is limited due to the transfer matrix element between substrate and adsorbate. In amorphous ice layers, this leads to sub-ps-lifetimes of the solvated electrons. These are initially injected into the ice conduction band before they start to stabilize 2.9eV above the Fermi level [1]. In contrast, we observe excess electrons within crystalline D2O/Ru(001) that present lifetimes up to several minutes before they relax back to the metal. Variation of the UV excitation energy shows that these electrons are transferred to the delocalized image potential state within the ice layer before they localize more than 2eV above the Fermi level into preformed traps. During their extremely long lifetime an increase of binding energy is observed, which is attributed to a re-arrangement of the polar environment. The notable temperature dependence of binding energy and photoelectron intensity will be discussed.
[1] U. Bovensiepen et al., Isr. J. Chem. 45 (2005), in press