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Detailed dynamics of a complex photochemical reaction: cis-trans photoisomerization of stilbene

Summary: Detailed dynamics of a complex photochemical reaction:
cis-trans photoisomerization of stilbene
Yusheng Dou and Roland E. Allen
Physics Department, Texas A&M University, College Station, TX 77843
(Dated: August 15, 2003)
Detailed simulations are reported for the dynamics of electrons and nuclei during the cis to
trans photoisomerization of stilbene. Our method, which employs a semiclassical description of
both the nuclear motion and the radiation field, is described in the text. After excitation of
electrons from the HOMO to the LUMO by a femtosecond-scale laser pulse, two principal avoided
crossings are observed between the HOMO and LUMO levels, each of which leads to substantial
depopulation of the LUMO. Based on our results and those of other groups, we propose that
the first such HOMO-LUMO coupling can lead to the formation of 4a,4b-dihydrophenanthrene
(DHP). The second coupling, on the other hand, leads to the formation of trans-stilbene. It is
found that pyramidalization of the two carbon atoms of the vinyl group is involved significantly in
both couplings, and that rotation of the two phenyl rings, together with their interaction, plays an
important role in the first coupling. The occurrence along the same trajectory of two couplings,
one leading to DHP and the other leading to isomerization, is a significant observation, and one
which indicates that further theoretical and experimental investigations would be of considerable


Source: Allen, Roland E. - Department of Physics and Astronomy, Texas A&M University


Collections: Physics