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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 28: Poster III
CPP 28.44: Poster
Wednesday, March 20, 2024, 11:30–13:30, Poster C
Intramolecular Barrier for Stilbene Photoisomerization from Temperature- and Viscosity-Dependent Transient Absorption — •Daria Schriever1, Alexander L. Dobryakov2, J. Luis Perez Lustres1, Martin Quick3, Ilya N. Ioffe4, and Sergey A. Kovalenko3 — 1Fachbereich Physik, Freie Universität Berlin — 2Moscow — 3Institut für Chemie, Humboldt Universität zu Berlin — 4Moscow
The photoisomerization of stilbene is investigated by means of fs broadband transient absorption in solution and compared to the RRKM and Kramers reaction rate theories [1]. To this end, it is necessary to extract the intramolecular barrier from the experimental one, which contains the viscosity contribution. Reaction dynamics is measured in a range of temperatures and non-polar solvents of various viscosities. In this way, the barrier height remains virtually unaffected by polar interactions between the surrounding solvent and the polar transition state of the isomerization reaction. In parallel, viscosity activation energies are obtained from the rotational diffusion times of the stilbene molecule. It is found that the isomerization time constant is proportional to ηα, with α=0.3. An average barrier of 1236 cm−1 is obtained, in good agreement with the gas phase results: 1398 cm−1 [2].
[1] S. A. Kovalenko, A. L. Dobryakov, Chem. Phys. Lett. 2013, 570, 56-60. [2] J. S. Baskin et al, J. Phys. Chem. 1996, 100, 11920-11933.
Keywords: femtosecond; isomerization; dynamics; RRKM; transient absorption