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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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Excited state wavepacket dynamics in NO2 probed by strong-field ionization.
Ruaridh Forbes1, Andrey E Boguslavskiy2, Iain Wilkinson2
1Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom.
The Journal of Chemical Physics
|August 10, 2017
Summary
We studied nitrogen dioxide's excited state dynamics using femtosecond time-resolved experiments. We observed oscillations and spectral features, revealing rapid ground state repopulation and vibrational energy spreading.
Area of Science:
- Physical Chemistry
- Chemical Physics
- Molecular Dynamics
Background:
- Understanding excited state dynamics is crucial for photochemistry and photophysics.
- Nitrogen dioxide (NO2) is a key molecule in atmospheric chemistry and combustion processes.
Purpose of the Study:
- To investigate the femtosecond excited state dynamics of nitrogen dioxide (NO2) following 399 nm photoexcitation.
- To probe ultrafast molecular dynamics using channel-resolved above threshold ionization (CRATI).
Main Methods:
- Femtosecond time-resolved spectroscopy utilizing pump-probe technique.
- Channel-resolved above threshold ionization (CRATI) with photoelectron-photoion coincidence.
- Covariance analysis to correlate photoelectron spectra with ionic fragments.
Main Results:
- Observed apparent oscillations in ion and photoelectron yields indicating dynamic processes.
- Detected a persistent above threshold ionization comb in photoelectron spectra at long delays.
- Identified signatures of higher-lying neutral state dynamics and rapid ground state repopulation (<200 fs).
- Observed evidence of intramolecular vibrational energy redistribution and ground state wavepacket spreading.
Conclusions:
- The study reveals complex dynamics including non-adiabatic coupling and vibrational energy redistribution in excited NO2.
- CRATI is a powerful technique for probing ultrafast molecular dynamics and state correlations.
- Vibrational energy spreading in the ground state allows exploration of nuclear geometries on the potential energy surface.
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