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Ethylene spectroscopy using a quasi-room-temperature quantum cascade laser
Stéphane Schilt1, Luc Thévenaz, E Courtois
1Metrology Laboratory, EPFL, Swiss Federal Institute of Technology, Lausanne. stephane.schilt@epfl.ch
Summary
Quantum cascade (QC) laser pulse duration broadens ethylene absorption spectra, affecting linewidth. Researchers determined this linewidth and achieved a 60 ppm detection limit using photoacoustic spectroscopy.
Area of Science:
- Spectroscopy
- Laser Physics
- Environmental Monitoring
Background:
- Ethylene detection is crucial for environmental and industrial applications.
- Quantum cascade (QC) lasers offer tunable mid-infrared light sources for gas sensing.
- Pulsed laser operation can introduce spectral broadening effects.
Purpose of the Study:
- To investigate the spectroscopic properties of ethylene using a quasi-room-temperature QC laser.
- To analyze the impact of laser pulse duration on spectral linewidth.
- To determine the detection limit of ethylene using photoacoustic (PA) spectroscopy.
Main Methods:
- Transmission spectroscopy measurements of ethylene using a pulsed QC laser (10.3 microm).
- Analysis of spectral broadening as a function of laser pulse duration (20-50 ns).
- Photoacoustic (PA) spectroscopy with a resonant PA cell for ethylene detection.
Main Results:
- Observed broadening of the ethylene absorption spectrum with increased laser pulse duration.
- Determined a laser linewidth of 0.04 cm(-1) at 20 ns pulse duration.
- Calculated an enhancement coefficient of 6.5 x 10(-3) cm(-1)/ns for linewidth increase.
- Achieved a detection limit of 60 ppm for ethylene using PA detection.
Conclusions:
- Laser pulse duration significantly influences spectral linewidth in QC laser spectroscopy.
- The characterized linewidth broadening is essential for accurate quantitative analysis.
- QC laser-based PA spectroscopy provides a sensitive method for ethylene detection.