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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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Strong Field Adiabatic Ionization Prepares a Launch State for Coherent Control
Timothy Bohinski1,2, Katharine Moore Tibbetts1,2, Maryam Tarazkar1,2
1†Department of Chemistry, Temple University, Philadelphia, Pennsylvania 19122, United States.
The Journal of Physical Chemistry Letters
|August 15, 2015
Summary
Strong field near-infrared pulses induce adiabatic ionization in acetophenone, enhancing parent ion signals and coherence time. This method offers improved control over molecular ionization dynamics compared to nonadiabatic ionization.
Area of Science:
- Physical Chemistry
- Femtochemistry
- Molecular Dynamics
Background:
- Acetophenone ionization dynamics are crucial for understanding molecular fragmentation.
- Strong field laser interactions offer precise control over chemical processes.
- Adiabatic vs. nonadiabatic ionization pathways influence molecular ion states.
Purpose of the Study:
- To investigate the effects of adiabatic ionization using near-infrared femtosecond pulses on acetophenone.
- To compare ionization dynamics induced by adiabatic and nonadiabatic pathways.
- To elucidate the mechanism of dissociation following adiabatic ionization.
Main Methods:
- Excitation of acetophenone using strong-field, near-infrared (1150-1500 nm) femtosecond pulses.
- Time-resolved probing of parent and fragment ions using a weak 790 nm pulse.
- Theoretical calculations including equation of motion coupled cluster and classical wavepacket trajectory simulations.
Main Results:
- Adiabatic ionization produced acetophenone radical cation in the ground electronic state.
- Observed an order of magnitude enhancement in peak-to-peak amplitude oscillations and a longer coherence time (~100 fs).
- Demonstrated an order of magnitude increase in the parent-to-fragment ion ratio compared to nonadiabatic ionization.
Conclusions:
- Adiabatic ionization with near-infrared pulses provides enhanced control over acetophenone ionization.
- The probe pulse excites a wavepacket to a higher electronic state, leading to dissociation.
- Direct population transfer to excited states can suppress wavepacket oscillations on the ground state.
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