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Updated: Jun 6, 2026

Measurement of Ultrafast Vibrational Coherences in Polyatomic Radical Cations with Strong-Field Adiabatic Ionization
Published on: August 6, 2018
Dynamics of highly excited nitroaromatics.
Bingxing Wang1, Benkang Liu, Yanqiu Wang
1State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Dalian 116023, China.
Highly excited nitroaromatics undergo ultrafast deactivation via internal conversion to Rydberg and ground states. Methyl substitution accelerates this process, with an ortho effect in o-nitrotoluene significantly enhancing the speed of nitroaromatic fragmentation.
Area of Science:
- Physical Chemistry
- Molecular Dynamics
- Photochemistry
Background:
- Extensive research exists on nitroaromatic photodissociation in low electronic states.
- Limited understanding of fragmentation dynamics in highly excited electronic states of nitroaromatics.
Purpose of the Study:
- Investigate the fragmentation dynamics of nitrobenzene, o-nitrotoluene, and m-nitrotoluene in highly excited states.
- Elucidate the ultrafast deactivation pathways and timescales involved.
Main Methods:
- Two-photon absorption at 271 nm to populate highly excited electronic states.
- Time-of-flight mass spectrometry to study fragmentation.
- One-photon ionization at 408 nm to monitor temporal evolutions of parent and fragment ions.
Main Results:
- Observed two ultrafast deactivation processes: internal conversion to Rydberg states (tens of femtoseconds) and to ground states (hundreds of femtoseconds).
- Methyl substitution accelerates the internal conversion process.
- Ortho effect in o-nitrotoluene, involving hydrogen transfer, significantly enhances deactivation rates.
Conclusions:
- Nitroaromatics in highly excited states exhibit rapid internal conversion pathways.
- Methyl substitution and intramolecular hydrogen transfer play crucial roles in modulating deactivation timescales.
- Provides insights into the fundamental photophysics of substituted nitroaromatics.
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