Regensburg 2025 – scientific programme

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BP: Fachverband Biologische Physik

BP 33: Focus Session Chemical Imaging for the Elucidation of Molecular Structure II (joint session O/BP)

BP 33.4: Talk

Friday, March 21, 2025, 11:45–12:00, H24

Elasticity Mapping of Nonahelicene with Submolecular Resolution by NC-AFM — •Max Halbauer¹, Takashi Kumagai², Martin Wolf¹, and Akitoshi Shiotari¹ — ¹Fritz-Haber-Institute, Faradayweg 4-6, 14195 Berlin, Germany — ²Institute for Molecular Science, 38 NishigoNaka, Myo-daiji, Okazaki 444-8585, Japan

Controlled modification of atomic configurations of molecules and materials is an exciting goal for non-contact atomic force microscopy (NC-AFM). Certain changes like shifts of the electronic energy gaps may be expected, but are not well explored and not established on the molecular scale. Here we report quantitative measurement of atomic-scale deformation in single molecules with NC-AFM. Individual molecules of nonahelicene ([9]H) and coronene (Cor) were studied on a Ag(110) surface under ultrahigh vacuum and cryogenic conditions by the measurement of frequency-shift distance curves for this. The molecular responses can be replicated with an empirical Lennard-Jones model, but for [9]H an elastic contribution is required to account for its elastic nature. Furthermore, a 3D-force mapping technique, termed molecular deformation mapping (MDM), allows to study the lateral position dependence of the elastic response. The MDM of [9]H reveals a spatially strongly anisotropic behaviour for the elasticity, interaction forces, elongation and binding energy of the tip to the molecule. The result is rationalized in terms of an aromaticity model.

Keywords: Elasticity; Helicene; Atomic Force Microscopy; Mapping; Aromaticity