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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 25: Molecular Electronics and Excited State Properties II
CPP 25.1: Talk
Wednesday, March 20, 2024, 09:30–09:45, H 0111
Solvent-Induced Isomerization in Stilbene. Possible Solution to a Longstanding Problem. — •J. Luis Perez Lustres1, Alexander L. Dobryakov2, Daria Schriever1, Martin Quick3, Ilya Ioffe4, and Sergey A. Kovalenko3 — 1Fachbereich Physik, Freie Universität Berlin — 2Moscow — 3Institut für Chemie, Humboldt Universität zu Berlin — 4Moscow
Stilbene isomerization reaction was studied in the gas phase at collisionless conditions and analysed by RRKM theory [1], which however fails to explain acceleration by buffer gas pressure [2]. In solution, RRKM provides no explanation for, a much faster rate and the small effect of excess excitation energy [3]. We revisited the problem with fs transient absorption in solution at λexc of 325 and 267 nm. The latter results in a molecular temperature of 600 K at time zero. Consistent with gas phase, an average barrier of 1236 cm−1 is deduced in nonpolar solvents. λexc-dependence is explained by complete IVR and vibrational cooling with a rate constant of 10 ps [4]. This is reconciled with RRKM theory by postulating an additional activation by the solvent, which would be dominant in solution.
References
[1] J. S. Baskin et al, J. Phys. Chem. 1996, 100, 11920-11933. [2] A. Meyer et al, J. Phys. Chem. A 1999, 103, 10528- 10539. [3] S. A. Kovalenko, A. L. Dobryakov, Chem. Phys. Lett. 2013, 570, 56-60. [4] S. A. Kovalenko et al, J. Chem. Phys. 2001, 115, 3256-3273.
Keywords: femtosecond; isomerization; dynamics; RRKM; transient absorption