Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 93: Plasmonics & Nanooptics VI: Near-Field Microscopy and Phenomena

O 93.9: Vortrag

Freitag, 5. April 2019, 12:30–12:45, H8

Near-Field Spectroscopy of Nanoscale Molecular Aggregates — Xing Gao and •Alex Eisfeld — MPI-PKS Dresden

When molecules are assembled into an aggregate, their mutual dipole-dipole interaction leads to electronic eigenstates that are coherently delocalized over many molecules. Knowledge about these states is important to understand the optical and transfer properties of the aggregates. Optical spectroscopy, in principle, allows one to infer information on these eigenstates and about the interactions between the molecules. However, traditional optical techniques using an electromagnetic field which is uniform over the relevant size of the aggregate cannot access most of the excited states because of selection rules.

We demonstrate that by using localized fields one can obtain information about these otherwise inaccessible states. As an example, we discuss in detail the case of local excitation via radiation from the apex of a metallic tip, which allows also scanning across the aggregate.The resulting spatially resolved spectra provide extensive information on the eigenenergies and wave functions.

[1] J. Phys. Chem. Lett. 9, 6003 (2018)