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Updated: Jul 29, 2026
10:52
Direct Imaging of Laser-driven Ultrafast Molecular Rotation
Published on: February 4, 2017
Excited state dynamics and rapid internal conversion in a stable dipole molecule
Gavin D Reid1, Douglas J Whittaker, Wolfgang Roth
1Department of Chemistry, University of Leeds, Woodhouse Lane, Leeds, UK LS2 9JT.
Summary
Azomethine ylides undergo rapid radiationless decay from their excited singlet state. This decay, driven by ring buckling rather than bond twisting, occurs before ground state relaxation.
Area of Science:
- Photochemistry
- Chemical Physics
- Molecular Dynamics
Background:
- Azomethine ylides, known as 'stable dipoles', are important in organic synthesis.
- Understanding excited-state dynamics is crucial for controlling photochemical reactions.
Purpose of the Study:
- To investigate the ultrafast excited-state relaxation mechanism of azomethine ylides.
- To elucidate the role of molecular geometry changes in the decay process.
Main Methods:
- Femtosecond laser excitation.
- Transient absorption spectroscopy.
- Solvent viscosity dependence studies.
Main Results:
- Excited singlet state exhibits ultrafast radiationless relaxation.
- Decay occurs via ring buckling, not C-N bond twisting.
- Ground state cooling observed with a 5.7 ps lifetime.
- Viscosity dependence of fluorescence is minimal.
Conclusions:
- The primary decay pathway from the excited state involves a significant geometric change (ring buckling).
- This mechanism differs from typical twisting dynamics observed in other fluorescent molecules.
- The excited state lifetime is 1.5 ps, with subsequent ground state relaxation.
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