Dresden 2006 – scientific programme

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O: Oberflächenphysik

O 43: Time-resolved spectroscopy I

O 43.4: Talk

Thursday, March 30, 2006, 18:15–18:30, WIL C207

Ultrafast interfacial electron transfer probed with two-photon photoemission — •Lars Gundlach, Ralph Ernstorfer, Silke Felber, Rainer Eichberger, and Frank Willig — Hahn-Meitner-Institute, Department: Dynamics of Interfacial Reactions SE4, Glienickerstrasse 100, 14109 Berlin

Two-photon photoemission (2PPE) is the method of choice for investigating ultrafast interfacial electron transfer because of its excellent sensitivity and time resolution. With this technique one can address adsorbates at coverages far below a monolayer. With the same chromophore perylene fixed with different anchor and bridge groups at the surface of rutile TiO₂(110) the corresponding 2PPE transients revealed the relevant parameters that characterize the contributing processes.
Instantaneous optical injection on one hand and slow injection over a long distance on the other hand were realized. Direct optical charge transfer was realized with the chromophore catechol that is known to form a charge transfer complex with Ti atoms on the surface of TiO₂. The slow injection cases were realized by inserting rigid molecular bridges. The same experimental systems were investigated with fs-transient absorption. Comparing the different 2PPE transients and the corresponding transient absorption transients for the identical systems revealed the physical processes and time scales that control the 2PPE transients. 2PPE measurements with different angle of incidents and polarizations of the pump pulse revealed the binding geometry of the different anchor groups on the surface.