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Photoelectron Imaging of Anions Illustrated by 310 Nm Detachment of F−
Published on: July 27, 2018
Vibrational Autodetachment and Valence-to-Nonvalence Population Transfer in the Nitromethane Anion
Sejun An1, Dabin Kim1, Sang Kyu Kim1
1Department of Chemistry, KAIST, Daejeon34141, Republic of Korea.
Vibrational Feshbach resonances in nitromethane anions are explored using time-resolved photoelectron spectroscopy. Autodetachment is limited by intramolecular vibrational redistribution, revealing new dynamics in electron-driven chemistry.
Area of Science:
- Physical Chemistry
- Chemical Physics
- Molecular Dynamics
Background:
- Vibrational Feshbach resonances (VFRs) are key to electron attachment and vibrational autodetachment in molecular anions.
- Real-time dynamics of VFRs in valence-bound radical anions are poorly understood due to experimental challenges with low electron affinities.
Purpose of the Study:
- Investigate the real-time dynamics of vibrational autodetachment in the nitromethane anion (CH3NO2-).
- Explore the role of intramolecular vibrational redistribution (IVR) in limiting autodetachment.
- Examine transient population transfer to dipole-bound states (DBS) induced by vibrational excitation.
Main Methods:
- Picosecond mid-infrared pump-probe photoelectron spectroscopy.
- Time-resolved photoelectron detection scheme to measure vibrational autodetachment lifetime.
- Selective excitation of the symmetric CH3 stretching mode.
Main Results:
- Determined a vibrational autodetachment lifetime of approximately 10 ps for CH3NO2-.
- Demonstrated that autodetachment is significantly slower than expected due to IVR.
- Observed transient population transfer from the valence-bound anion to a dipole-bound state (DBS).
Conclusions:
- VFRs in valence-bound radical anions act as dynamical gateways, not just precursors to electron emission.
- Autodetachment is limited by IVR, which delays electron emission.
- Mode-selective vibrational excitation can induce reverse internal conversion to DBS, influencing electron relaxation pathways.
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