Diode laser measurement of line strengths and air-broadening coefficients of CO₂ and CO in the 1.57 μm region for combustion diagnostics

Abstract

Spectral measurements of two line pairs of CO₂ and CO in the temperature range 300–1000 K at 1.573 µm were performed using a fiber-coupled distributed feedback (DFB) diode laser. The two line pairs can be used in a tunable diode laser (TDL) absorption sensor for simultaneously detecting CO₂ and CO gas in a single scan of the diode laser. The spectral parameters (line strengths, air-broadening coefficients and the temperature exponent n) of the two pairs are presented. The measured data agree well with existing databases (HITRAN 2004 and HITRAN 2008), the discrepancies being less than 5% for most of the probed transitions. Although the HITRAN database is a useful tool for sensor design, we found that laboratory measurements of the spectroscopic data for the line pair selected for high-temperature sensors are necessary for establishing the uncertainty for accurate measurements.

Keywords:

• CO₂ and CO
• high temperature
• line strength
• air-broadening coefficients

Acknowledgements

This research was funded by the National 863 High Technology Research and Development Program of China under grant No. 2006AA06Z237, and the French International Program of Scientific Cooperation (CNRS/PICS No. 3359). The authors are most grateful to Dr. Weixiong Zhao, Dr. Zhensong Cao and Dr. Kun Liu for their help with certain stages of this work, for helpful discussions and for useful recommendations.