Erlangen 2018 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 15: Complex Systems in the Gas Phase

MO 15.5: Vortrag

Mittwoch, 7. März 2018, 15:00–15:15, PA 1.150

Demystifying the azobenzene trans-cis isomerization process — •Mario Niebuhr, Axel Heuer, and Markus Gühr — Institute for Physics and Astronomy, Uni Potsdam, Germany

Azobenzene is a model system for photo-addressable switches both in chemistry and physics. The characteristic trans-cis isomerization, a fully reversible reorganization of the molecule‘s configuration under VIS/UV irradiation, is extensively used from addressable dyes to control systems for e. g. alignment of liquid crystal films in polarization switches. Albeit a decades long history of investigation and an intensive theoretical discussion in the 2000s, fundamental questions about the exact process remain such as the mechanism (inversion, torsion, bond bending), the origin of the Kasha rule violation upon S2 excitation or a precise timeline.

We perform ultra-fast pump-probe spectroscopy on isolated azobenzene molecules in the gas phase, yielding time-resolved data free of environmental influences and therefore especially compatible with high-level ab-initio calculations. A commercial 100 kHz Yb:KGW system supplies ultra-short pulses from the NIR fundamental to UV harmonics, used for ion time-of-flight spectroscopy and soon transient absorption. First data will be presented and further planned experiments as well as their possible contribution to the azobenzene debate discussed, such as synchrotron UV excited fragmentation studies and pump-probe electron diffraction.