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Updated: Aug 15, 2026

Novel Techniques for Observing Structural Dynamics of Photoresponsive Liquid Crystals
Published on: May 29, 2018
Ultrafast relaxation in quasi-one-dimensional organic molecular crystals
E Engel1, M Koschorreck, K Leo
1Institut für Angewandte Photophysik, Technische Universität Dresden, D-01062 Dresden, Germany.
Abstract:
We present a comprehensive study of ultrafast relaxation properties of optical excitations in thin films of quasi-1D stacked organic materials PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride) and MePTCDI (N,N'-dimethylperylene-3,4,9,10-dicarboximide) over five decades of time. Pump-probe experiments reveal excitonic intraband relaxation time constants of 65 fs for MePTCDI and 100 fs for PTCDA. The initial time-resolved luminescence anisotropy is consistent with the exciton model of Davydov-split states. The subsequent decay of the anisotropy can be explained with a thermally activated exciton hopping process. A full understanding of the pump-probe experiments calls for an explanation beyond the models presently available.
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