Transient Stimulated Raman Excited Fluorescence Spectroscopy

Area of Science:

• Optics and Spectroscopy
• Chemical Physics
• Molecular Spectroscopy

Background:

• Raman spectroscopy aims for enhanced sensitivity, crucial for molecular analysis.
• Current single-molecule Raman spectroscopy methods face challenges with fluorescence backgrounds and excitation.
• Existing frequency-domain techniques lack efficient hyperspectral excitation.

Purpose of the Study:

• To develop an ultrafast time-domain spectroscopy method for background-free Raman spectra.
• To overcome limitations of existing frequency-domain Raman spectroscopy.
• To achieve high sensitivity for molecular detection and dynamics sensing.

Main Methods:

• Introduced transient stimulated Raman excited fluorescence (T-SREF), an ultrafast time-domain technique.
• Utilized two successive broadband femtosecond pulse pairs (pump and Stokes pulses) with time-delay scanning.
• Applied Fourier transform to time-domain fluorescence traces revealing vibrational wave packet interference.

Main Results:

• T-SREF successfully generated background-free Raman spectra of electronic-coupled vibrational modes.
• Achieved sensitivity at the level of a few molecules.
• Demonstrated vibrational wave packet interference in time-domain fluorescence.

Conclusions:

• T-SREF offers a powerful alternative to frequency-domain Raman spectroscopy.
• The method enables supermultiplexed fluorescence detection and molecular dynamics sensing.
• T-SREF significantly advances the sensitivity and applicability of Raman spectroscopy.