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Blue-Shifted and Broadened Fluorescence Enhancement by Visible and Mode-Selective Infrared Double Excitations
Qirui Yu1, Xinmao Li1, Chengzhen Shen1
1College of Chemistry and Molecular Engineering, Beijing National Laboratory for Molecular Sciences, Peking University, Beijing 100871, China.
The Journal of Physical Chemistry. A
|April 4, 2024
Summary
Mode-selective vibrational excitations using visible and infrared pulses enhance fluorescein dianion fluorescence. This study reveals how vibrational excitations and relaxations significantly modify luminescence properties.
Area of Science:
- Physical Chemistry
- Spectroscopy
- Photophysics
Background:
- Fluorescein dianion fluorescence is sensitive to its molecular environment.
- Understanding excited-state dynamics is crucial for photophysical applications.
- Mode-selective vibrational control offers a pathway to tune molecular properties.
Purpose of the Study:
- To investigate the effects of synchronized visible and infrared (IR) pulses on fluorescein dianion fluorescence.
- To elucidate the mechanisms behind fluorescence intensity enhancement, peak blueshift, and line width broadening.
- To explore the role of vibrational excitations and relaxations in modifying luminescence.
Main Methods:
- Femtosecond visible pulse synchronized with a picosecond IR pulse for double resonance experiments.
- Scanning vibrational excitation frequencies and tuning time delays between pulses.
- Nonlinear and linear spectroscopic measurements.
- Theoretical calculations.
Main Results:
- Simultaneous enhancement of fluorescence intensity, peak blueshift, and line width broadening were observed.
- Fluorescence enhancement is attributed to increased Franck-Condon factors from ground-state vibrational excitations.
- Blueshift and broadening result from increased Franck-Condon factors and long-lived processes induced by IR pre-excitation.
- Vibrational relaxations significantly influence luminescence modification.
Conclusions:
- Fluorescence modulation via visible/IR double resonance is not a simple sum frequency effect.
- Vibrational excitations and subsequent relaxations profoundly impact molecular luminescence.
- This work demonstrates a method for controlling and understanding photophysical processes through vibrational mode selectivity.
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