Regensburg 2004 – wissenschaftliches Programm

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O: Oberflächenphysik

O 37: Zeitaufgelöste Spektroskopie I

O 37.7: Vortrag

Donnerstag, 11. März 2004, 17:15–17:30, H36

Femtosecond electron dynamics in amorphous and crystalline ice layers on Ru(001) — •Martin Wolf, Cornelius Gahl, Julia Stähler, Panagiotis Loukakos, and Uwe Bovensiepen — Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195 Berlin

The ultrafast electron transfer and solvation dynamics in D2O layers on Ru(001) have been studied by time-resolved two-photon-photoemission (2PPE) spectroscopy. Structural characterization of the ice layers were carried out by simultaneous measurements of the electronic structure, work function and the D2O desorption rate as a function of temperature. Hereby, amorphous and crystalline multilayers as well as the bilayer can be prepared with high accuracy. We find that the electron dynamics differ significantly for amorphous and crystalline ice. In amorphous layers, electron solvation, characterized by a time-dependent shift of the electron binding energy by 1 eV/ps, as well as the population decay, occurs much faster compared to the dynamics observed previously in amorphous D2O layers on Cu(111) [1]. This is attributed to structural differences of the first bilayer and more efficient electron backtransfer to the Ru substrate. Moreover, the binding energy of the solvated state increases at a higher rate on the Ru substrate suggesting a more mobile hydrogen bonded network than on Cu. In the crystalline ice layers electron solvation is not been observed, however, trapping of extremly long-lived electrons into structural defects formed by thermal activation.

[1] Phys. Rev. Lett. 89, 107402 (2002); J. Phys. Chem. B 107, 8706 (2003).

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