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Updated: Feb 1, 2026

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Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization
Published on: August 6, 2018
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Ultrafast solvent-to-solute proton transfer mediated by intermolecular coherent vibrations
Ramesh Jarupula1, Yuezhi Mao2, Haiwang Yong3,4
1Department of Chemistry, University of California, San Diego, La Jolla, CA, USA.
Communications Chemistry
|January 30, 2026
Summary
Ultrafast excited-state proton transfer (ESPT) in PBI/methanol involves rapid proton transfer and energy dissipation. Vibrational modes coupled to methanol influence the anharmonic potential energy surface during ESPT.
Area of Science:
- Photochemistry
- Chemical Physics
- Biomolecular Science
Background:
- Ultrafast excited-state proton transfer (ESPT) is vital for biomolecule and material photoprotection.
- Understanding solute-solvent interactions in ESPT dynamics is crucial but challenging.
Purpose of the Study:
- To investigate the ultrafast ESPT dynamics of 2-(2´-pyridyl)benzimidazole (PBI) in methanol.
- To elucidate the role of solute-solvent interactions and vibrational coherences in ESPT.
Main Methods:
- Ultrafast absorption spectroscopy.
- Quantum chemical calculations.
- Femtosecond-resolved dynamics and Fourier analysis.
Main Results:
- Identified three kinetic steps: 2.2 ps proton transfer, 31 ps nonradiative relaxation, and 186 ps energy equilibration.
- Observed coherent wavepacket motion on the S1 potential energy surface with dominant vibrational periods of ~117 fs and ~340 fs.
- Confirmed anharmonic potential energy surface evolution due to rapid dephasing (<300 fs).
Conclusions:
- Solute-solvent interactions significantly influence ESPT dynamics in PBI/methanol.
- Coupled vibrational modes of PBI and methanol drive the ESPT reaction coordinate on an anharmonic surface.
- ESPT involves complex dynamics including vibrational coherences and rapid energy dissipation.
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