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Direct Imaging of Laser-driven Ultrafast Molecular Rotation
Published on: February 4, 2017
Pump-degenerate four wave mixing as a technique for analyzing structural and electronic evolution: multidimensional
Jürgen Hauer1, Tiago Buckup, Marcus Motzkus
1Physikalische Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse, D-35043 Marburg, Germany.
The Journal of Physical Chemistry. A
|October 5, 2007
Summary
Pump-degenerate four-wave mixing (pump-DFWM) reveals ultrafast dynamics in all-trans-beta-carotene. This method tracks structural and electronic changes during excited-state transitions, offering insights into internal conversion processes.
Area of Science:
- * Physical Chemistry
- * Spectroscopy
- * Ultrafast Dynamics
Background:
- * Understanding excited-state dynamics is crucial for controlling photochemical reactions.
- * Non-adiabatic passages between electronic states involve complex structural and electronic evolutions.
- * All-trans-beta-carotene serves as a model system for studying these phenomena due to its interesting photophysics.
Purpose of the Study:
- * To simultaneously investigate the early structural and electronic population dynamics during non-adiabatic transitions.
- * To comprehensively describe the S2 --> S1 internal conversion process in all-trans-beta-carotene.
- * To explore the potential of pump-degenerate four-wave mixing for coherent control of excited-state dynamics.
Main Methods:
- * Utilized pump-degenerate four-wave mixing (pump-DFWM) to probe excited-state dynamics.
- * Employed a pump beam to populate the S2 state, followed by a DFWM sequence resonant with the S1 --> Sn transition.
- * Achieved 20 fs temporal and 10 cm-1 spectral resolution for observing excited-state mode evolution.
Main Results:
- * Observed ultrafast dynamics between the 1Bu+ (S2) and 2Ag- (S1) states in all-trans-beta-carotene.
- * Provided a detailed analysis of vibrational cooling on the S1 state.
- * Characterized a low-lying, vibrationally hot excited state, offering insights into conical intersection dynamics.
Conclusions:
- * Pump-DFWM effectively captures both vibrational dynamics and ultrafast electronic spectroscopy near conical intersections.
- * The technique provides a comprehensive picture of the S2 --> S1 internal conversion in all-trans-beta-carotene.
- * Pump-DFWM offers a promising route for ultrafast coherent control of excited-state molecular dynamics.
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