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Updated: Jul 11, 2025

High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy
Published on: June 28, 2016
Vibrationally Resolved Absorption, Fluorescence, and Preresonance Raman Spectroscopy of Isolated Pyronin Y Cation at
Sreekanta Debnath1, Alexander Schäfer1, Shun Ito2
1Institute of Physical Chemistry II, Karlsruhe Institute of Technology, Fritz-Haber-Weg 2, 76131 Karlsruhe, Germany.
Charge-changing significantly impacts organic dye photoluminescence. Researchers compared pyronin Y cation and its neutral radical, finding the cation emits light while the radical does not, confirmed by spectroscopy and theory.
Area of Science:
- Photochemistry and Photophysics
- Spectroscopy
- Computational Chemistry
Background:
- Understanding charge-state effects on organic dye photoluminescence is crucial but challenging.
- Small organic dyes are vital in various imaging and sensing applications.
Purpose of the Study:
- To investigate and compare the photophysical properties of pyronin Y cation ([PY]+) and its neutral radical ([PY]•).
- To elucidate the influence of charge state on visible photoluminescence.
Main Methods:
- Helium tagging photodissociation (PD) action spectroscopy in the gas phase.
- Dispersed laser-induced fluorescence (DF) spectroscopy in a solid Neon matrix at 5 K.
- Time-Dependent Density-Functional Theory (TD-DFT) calculations using the FCHT method (B3LYP/aug-cc-pVDZ).
Main Results:
- The pyronin Y cation ([PY]+) exhibits efficient visible photoluminescence.
- No emission was detected from the one-electron-reduced neutral radical ([PY]•), aligning with theoretical predictions.
- Vibrationally resolved absorption and emission spectra were assigned using TD-DFT/FCHT calculations.
- Electronic preresonance Raman (ePR-Raman) spectra of [PY]+ were observed with a significant efficiency factor.
Conclusions:
- The study clarifies the distinct photophysical behaviors of charged and neutral organic dye species.
- The observed properties of the [PY]•/[PY]+ pair suggest potential for functionalized derivatives in bioimaging and stimulated-Raman spectroscopies.
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