Fluorescence-Detected Pump-Probe Spectroscopy for Artifact-Free Detection of Stokes Shift Dynamics

Area of Science:

• Ultrafast spectroscopy
• Photochemistry
• Physical chemistry

Background:

• Excited-state dynamics are crucial for understanding photochemical processes.
• Conventional transient absorption (TA) spectroscopy faces challenges with signal overlap and artifacts.
• Fluorescence-detected pump-probe (F-PP) spectroscopy combines high temporal resolution with sensitive fluorescence detection.

Purpose of the Study:

• To demonstrate inherently phase-stable F-PP spectroscopy for studying ultrafast excited-state dynamics.
• To showcase the advantages of F-PP over conventional TA spectroscopy.
• To investigate the ultrafast Stokes shift dynamics of a solvated fluorophore.

Main Methods:

• Utilized 20 fs pulses for F-PP spectroscopy.
• Employed quantitative signal background subtraction.
• Compared F-PP results with conventional TA spectroscopy.

Main Results:

• Observed ultrafast Stokes shift dynamics with a time constant of 84 fs.
• F-PP provided a coherent artifact-free view of the stimulated emission process.
• Demonstrated signal isolation, revealing pure stimulated emission spectra, unlike overlapping signals in TA.

Conclusions:

• Phase-stable F-PP spectroscopy is a powerful technique for studying excited-state dynamics.
• F-PP offers superior signal clarity and isolation compared to TA spectroscopy.
• This method enables a more accurate investigation of ultrafast spectral shifts.