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O: Fachverband Oberflächenphysik

O 44: Ultrafast Electron Dynamics II (joint session O/MA)

O 44.8: Vortrag

Dienstag, 17. März 2020, 12:45–13:00, WIL B321

Momentum resolved ultrafast organic molecular exciton dynamics — •Ralf Hemm, Martin Mitkov, Florian Haag, Sebastian Emmerich, Sebastian Hedwig, Martin Aeschlimann, and Benjamin Stadtmüller — University of Kaiserslautern (TUK) and research center OPTIMAS, Erwin-Schroedinger-Str.46, 67663 Kaiserslautern, Germany

Mapping the lowest unoccupied molecular orbitals (LUMOs) of an organic semiconducting thin film in momentum space is one of the great challenges of ultrafast surface science. Especially on the femto- to picosecond timescale, resolving the transient molecular orbital structure can help to disentangle excitonic decay mechanisms.

Here, we apply bichromatic time-resolved two-photon momentum microscopy [1] to image the excited state dynamics of excitons in molecular materials in momentum space. Our model system is a multilayer of ordered C60 on Cu(111), for which the energy dependent exciton dynamics was already reported in literature [2]. In this talk, we will therefore focus on the momentum space signatures of the excited states. We will identify the characteristic momentum space signatures of the excited states and follow their evolution above and below the critical temperature for the structural phase transition of C60. This will allow us to correlate the exciton dynamics in momentum space to the dominant energy and momentum dissipation process in molecular materials.

[1] F. Haag et al., Rev. Sci. Instr. 90, 103104 (2019)

[2] A. Rosenfeldt et al., J. Chem. Phys. 133, 23 (2010)