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O: Fachverband Oberflächenphysik

O 99: Post-Deadline Session

O 99.2: Vortrag

Donnerstag, 21. März 2024, 19:42–19:54, H 0105

Taking Swings at Springs or How Soft is a Molecule? — •Max Halbauer¹, Takashi Kumagai², Martin Wolf¹, and Akitoshi Shiotari¹ — ¹Fritz-Haber-Institute, Faradayweg 4-6, 14195 Berlin, Germany — ²Institute for Molecular Science, 38 NishigoNaka, Myodaiji, Okazaki 444-8585, Japan

Atomic force microscopy (AFM) provides fascinating insights into the properties and reactions of molecules and atoms on surfaces. But one of the most fundamental properties - the elasticity of molecules - has evaded detailed investigation.

This contribution explores how "taking swings" at individual spring-like molecules allows the characterisation of their softness. The age-old Hooke's law is found to be suitable for interpreting a modern day AFM experiment. The study of individual [9]Helicene molecules shows that their spring constant for elongation is 5-6 N/m. Through systematic mapping experiments it is even possible to resolve their elastic response with submolecular resolution. Strikingly, these measurements reveal a strongly anisotropic behaviour for the molecules interaction with scanning probe microscopy tips. This work thus builds a bridge from our experience of the macroscopic world to the microscopic domain. It leads us to an important conclusion: Molecules and atoms are commonly portrayed as hard spheres and sticks, but the reality is different. The question "How soft is a molecule?" must be answered with: Molecules are super soft!

Keywords: molecular elasticity; atomic force microscopy; frequency shift distance measurements; helicene; Hooke's law