Dresden 2026 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 12: Scanning probe microscopy: light matter interaction at atomic scales

O 12.8: Vortrag

Montag, 9. März 2026, 16:45–17:00, HSZ/0403

Selectivity in tautomerization reaction pathways triggered in single molecules on ultrashort time scales — •Niklas Friedrich, Carmen Roelcke, Tzu-Chao Hung, Yaroslav Gerasimenko, Rupert Huber, and Jascha Repp — Institute of Experimental and Applied Physics and Regensburg Center for Ultrafast Nanoscopy (RUN), University of Regensburg, and Halle-Berlin-Regensburg Cluster of Excellence CCE, Germany

Lightwave-driven scanning tunnelling microscopy (LW-STM) is a powerful technique allowing to unravel dynamics of quantum systems on their intrinsic energy, spatial and temporal scales [1,2]. In LW-STM, the electric-field transient of ultrashort laser pulses focused into the junction of a tunnelling microscope acts as a bias-voltage transient and thereby controls tunnelling on ultrashort timescales.

Here, we explore a chemical reaction triggered on ultrashort timescales. We study free-base naphthalocyanine molecules (H2Nc) on 2ML NaCl on Cu(100). In DC-biased experiments, this system switches between different tautomers upon injection of high-energy tunnelling electrons [3]. We find that the same reaction is facilitated by ultrashort voltage transients in LW-STM for transients far exceeding the voltage of the lowest unoccupied molecular orbital. Furthermore, we observe different selectivities in the tautomerization reaction depending on the energy of the tunnelling electron that we tentatively assign to the orbital structure of H2Nc.

[1] Nat. Photon. 18, 595-602 (2024) [2] arXiv:2507.10206 (2025) [3] Science 317, 1203-1206 (2007)

Keywords: lightwave-driven STM (LW-STM); ultrashort; scanning tunnelling microscopy (STM); single molecule