Regensburg 2019 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 46: Ultra-fast phenomena

HL 46.4: Vortrag

Freitag, 5. April 2019, 10:15–10:30, H31

Transient absorption and population dynamics of laser-excited conjugated molecules from RT-TDDFT — •Jannis Krumland¹, Ana Valencia¹, Stefano Pittalis², Carlo Andrea Rozzi², and Caterina Cocchi¹ — ¹Physics Dept. and IRIS Adlershof, Humboldt-Universität zu Berlin, Germany — ²CNR NANO, Modena, Italy

Pump-probe spectroscopy is a powerful tool to study the electronic and optical properties of materials. In transient absorption spectroscopy, the system is illuminated by two femtosecond laser pulses with the first one exciting the system and the second one probing its response at a given time delay. Real-time time-dependent density functional theory (RT-TDDFT) can be adopted for ab- initio simulations of these experiments [1]. In RT-TDDFT, the electron density is propagated in time, enabling the calculation of optical properties in the linear regime and beyond. We apply this method to investigate ethylene, benzene and thiophene molecules representing the building blocks of a variety of organic compounds. By applying laser pulses of increasing intensity in resonance with the gap transition, we analyze the dynamics of photo-excited electrons. From the transient absorption spectra, we identify the signatures of excitations due to the laser-induced population of initially unoccupied states. The underlying mechanisms of excited-state absorption are discussed in relation with benchmark calculations unraveling their excitations in the linear response [2].

[1] U. de Giovannini et al., ChemPhysChem 14 1363 (2013)

[2] J. Krumland et al., in preparation (2019)