Matches in SemOpenAlex for { <https://semopenalex.org/work/W3087334400> ?p ?o ?g. }
- W3087334400 endingPage "9046" @default.
- W3087334400 startingPage "9029" @default.
- W3087334400 abstract "Carotenoids are usually only weakly fluorescent despite being very strong absorbers in the mid-visible region because their first two excited singlet states, S1 and S2, have very short lifetimes. To probe the structural mechanisms that promote the nonradiative decay of the S2 state to the S1 state, we have carried out a series of fluorescence lineshape and anisotropy measurements with a prototype carotenoid, β-carotene, in four aprotic solvents. The anisotropy values observed in the fluorescence emission bands originating from the S2 and S1 states reveal that the large internal rotations of the emission transition dipole moment, as much as 50° relative to that of the absorption transition dipole moment, are initiated during ultrafast evolution on the S2 state potential energy surface and persist upon nonradiative decay to the S1 state. Electronic structure calculations of the orientation of the transition dipole moment account for the anisotropy results in terms of torsional and pyramidal distortions near the center of the isoprenoid backbone. The excitation wavelength dependence of the fluorescence anisotropy indicates that these out-of-plane conformational motions are initiated by passage over a low-activation energy barrier from the Franck–Condon S2 structure. This conclusion is consistent with detection over the 80–200 K range of a broad, red-shifted fluorescence band from a dynamic intermediate evolving on a steep gradient of the S2 state potential energy surface after crossing the activation barrier. The temperature dependence of the oscillator strength and anisotropy indicate that nonadiabatic passage from S2 through a conical intersection seam to S1 is promoted by the out-of-plane motions of the isoprenoid backbone with strong hindrance by solvent friction." @default.
- W3087334400 created "2020-09-25" @default.
- W3087334400 creator A5006938084 @default.
- W3087334400 creator A5030716766 @default.
- W3087334400 creator A5046097833 @default.
- W3087334400 creator A5050657318 @default.
- W3087334400 creator A5065227395 @default.
- W3087334400 creator A5075410289 @default.
- W3087334400 creator A5077667571 @default.
- W3087334400 date "2020-09-21" @default.
- W3087334400 modified "2023-10-18" @default.
- W3087334400 title "Fluorescence Anisotropy Detection of Barrier Crossing and Ultrafast Conformational Dynamics in the S<sub>2</sub> State of β-Carotene" @default.
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