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Published on: October 30, 2012
Evidence for a Twisted Intermediate in Gaseous Uracil Revealed by Photoelectron Quantum Beats
Shutaro Karashima1, Toshinori Suzuki1
1Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-Ku, Kyoto 606-8502, Japan.
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Recent theoretical and experimental investigations have identified the formation of a previously unrecognized intermediate characterized by a strongly twisted C5=C6 double bond in the ground electronic state of pyrimidine nucleobases in an aqueous solution. This intermediate is produced by ultrafast internal conversion, representing a critical pathway in the photophysics of nucleobase relaxation. Nevertheless, the existence of such a species under gas-phase conditions has not yet been confirmed. In this study, we present the first direct experimental evidence for the formation of twisted intermediates in isolated molecules. Analysis of vibrational quantum beats observed using extreme ultraviolet time-resolved photoelectron spectroscopy reveals the presence of this transient species in the gas phase, further confirming that its formation is an intrinsic property of the nucleobase chromophore.
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