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O: Fachverband Oberflächenphysik

O 67: Poster Session V: Ultrafast electron dynamics at surface and interfaces I

O 67.2: Poster

Wednesday, March 3, 2021, 10:30–12:30, P

The ambivalent competition of Coulomb and van-der-Waals interactions in Xe-Cs⁺ aggregates on Cu(111) surfaces — •John Thomas¹, Cord Bertram^1,2, Janos Daru², Ping Zhou¹, Dominik Marx², Karina Morgenstern², and Uwe Bovensiepen¹ — ¹Physik, Universität Duisburg-Essen — ²Chemie, Ruhr-Universität Bochum

The properties of heterogeneous interfaces are important because of their fundamental and technological perspectives. We aim at understanding the contributions of the Coulomb and van-der-Waals interactions in Xe-Cs⁺ aggregates on Cu(111). By combining time-resolved Two-Photon Photoelectron Spectroscopy (2PPE), Scanning Tunneling Microscopy (STM), and coupled cluster calculations, we investigate the microscopic structure and the ultrafast dynamics excited by photo-induced electron transfer. We observe by time-resolved 2PPE that adsorption of Xe results in a fivefold increase of the Cs 6s electron lifetime, an effect attributed to the repulsion of the Cs 6s wave function by the electron density of Xe. Furthermore, we observe by STM that the Cs⁺...Cs⁺ distance shrinks from 2-7 nm to 1-3 nm for the aggregates compared to bare Cs⁺/Cu(111). The adsorption of Xe on Cs/Cu(111) results in a dual, i.e. attractive or repulsive, response of Xe depending on the positive or negative charge of the respective counterparticle, which emphasizes the dominant role of the Coulomb interaction between an alkali and a noble gas atom on the Cu(111).

This work was supported by the Cluster of Excellence RESOLV, funded by the Deutsche Forschungsgemeinschaft.