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Multiphoton photochemical and collisional effects during oxygen-atom flame detection
Optics Letters
|September 2, 2009
Summary
This study used laser-based two-photon excitation to probe oxygen atoms in flames. The laser technique proved intrusive, potentially creating atoms via multiphoton photolysis.
Area of Science:
- Combustion Chemistry
- Laser Spectroscopy
- Atomic Physics
Background:
- Understanding combustion processes requires accurate in-situ diagnostics.
- Laser-based techniques offer non-intrusive methods for species detection.
- Two-photon excitation is a sensitive method for probing atomic species.
Purpose of the Study:
- To investigate the use of two-photon laser excitation for probing oxygen atoms in flames.
- To analyze the emission spectra resulting from excited oxygen atoms.
- To assess the potential intrusiveness of the laser diagnostic method.
Main Methods:
- A Nd:YAG-pumped dye laser system was employed for two-photon excitation.
- Oxygen atoms were excited at 225.6 nm in an atmospheric-pressure flame (CH4-N2O-N2).
- Emissions at 844.7 nm and 777.5 nm were monitored, along with O and H atom emissions.
Main Results:
- Direct emission from the populated oxygen state was observed at 844.7 nm.
- A stronger emission at 777.5 nm resulted from collisional energy transfer.
- Two-photon resonant O and H atom emissions occurred in the absence of flame due to laser-induced photolysis.
Conclusions:
- Two-photon laser excitation can probe oxygen atoms in flames.
- The laser probe can be intrusive, inducing multiphoton photolysis of fuel and oxidizer molecules.
- Careful consideration of laser energy and probed region is necessary for accurate combustion diagnostics.
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