Dresden 2026 – scientific programme
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O: Fachverband Oberflächenphysik
O 43: Scanning probe microscopy: light matter interaction at atomic scales – Poster
O 43.3: Poster
Tuesday, March 10, 2026, 14:00–16:00, P2
Photoisomerization of azobenzene derivatives on Au (111) using various photon energies and polarizations — •Haraprasad Mandal1, Paul Schöngrundner1, Stefan Hecht2, and Leonhard Grill1 — 1Department of Chemistry, University of Graz, Austria — 2Department of Chemistry, Humboldt-Universität zu Berlin, Germany
Azobenzene derivatives continue to serve as model systems for studying photoisomerization at surfaces. Among them, tetra-tert-butyl azobenzene (TBA) is particularly suitable due to its chemical stability, large steric groups, and well-defined trans and cis configurations that can easily be identified in scanning tunnelling microscopy (STM) images. In this work, we systematically studied the photon-energy- and polarization-dependent trans-to-cis isomerization of TBA, using a tunable femtosecond laser in combination with STM (working in ultrahigh vacuum and at low temperatures). Illumination is done through an optical port, and STM imaging is used to identify the configuration of individual molecules before and after laser exposure. The switching efficiency was then studied for a variety of wavelengths in the range between 350 nm and 800 nm as well as different (s/p) polarization directions of the incoming light. Our results provide direct insight into the parameters that steer TBA photoisomerization on Au(111) and demonstrate the capability of our laser STM platform for controlled photochemical studies of single molecules.
Keywords: Scanning tunneling microscopy; Photoisomerization of azobenzene; Ultrafast laser