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Spectrally-tunable femtosecond single-molecule pump-probe spectroscopy
Optics Express
|October 7, 2021
Summary
Single-molecule pump-probe spectroscopy reveals distinct relaxation pathways in fluorescent dyes. This technique uncovers spectrally-independent, bimodal distributions for electronic dephasing and vibrational relaxation, indicating minimal molecular heterogeneity.
Area of Science:
- Physical Chemistry
- Spectroscopy
- Materials Science
Background:
- Single-molecule spectroscopy investigates molecular heterogeneity on millisecond to second timescales.
- Single-molecule pump-probe spectroscopy extends this capability to femtosecond and picosecond timescales.
Purpose of the Study:
- Develop a spectrally-tunable single-molecule pump-probe apparatus.
- Investigate energetic relaxation dynamics in the fluorescent dye Atto647N.
Main Methods:
- Utilized a newly developed, spectrally-tunable single-molecule pump-probe setup.
- Analyzed relaxation time constants of individual Atto647N molecules.
Main Results:
- Observed a spectrally-independent, bimodal distribution of relaxation time constants.
- Identified two dominant relaxation processes: electronic dephasing (~100 fs) and intravibrational relaxation (~300 fs).
- Found narrow distributions for both processes, suggesting limited heterogeneity.
Conclusions:
- The bimodal distribution indicates that individual molecules are dominated by a single relaxation pathway.
- Spectrally-tunable single-molecule pump-probe spectroscopy is a powerful tool for studying heterogeneity in diverse systems.
- This technique opens avenues for investigating biological and material science applications.
