A Detection Technique for Gas Concentration Based on the Spectral Line Shape Function
ZHOU Mo1, YANG Bing-chu1, TAO Shao-hua1, 2*
1. School of Physics and Electronics, Central South University, Changsha 410083, China 2. Institute of Super Microstructure and Ultrafast Process in Advanced Materials, School of Physics & Electronics, Central South University, Changsha 410083, China
Abstract：The methods that can rapidly and precisely measure concentrations of various gases have extensive applications in the fields such as air quality analysis, environmental pollution detection, and so on. The gas detection method based on the tunable laser absorption spectroscopy is considered a promising technique. For the infrared spectrum detection techniques, the line shape function of an absorption spectrum of a gas is an important parameter in qualitative and quantitative analysis of a gas. Specifically, how to obtain the line shape function of an absorption spectrum of a gas quickly and accurately is a key problem in the gas detection fields. In this paper we analyzed several existing line shape functions and proposed a method to calculate precisely the line shape function of a gas, and investigated the relation between the gas concentration and the peak value of a line shape function. Then we experimentally measured the absorption spectra of an acetylene gas in the wavelength range of 1 515～1 545 nm with a tunable laser source and a built-in spectrometer. With Lambert-Beer law we calculated the peak values of the line shape function of the gas at the given frequencies, and obtained a fitting curve for the line shape function in the whole waveband by using a computer program. Comparing the measured results with the calculated results of the Voigt function, we found that there was a deviation between the experimental results and the calculated results. And we found that the measured concentration of the acetylene gas by using the fitting curve of the line shape function was more accurate and compatible with the actual situation. Hence, the empirical formula for the line shape function obtained from the experimental results would be more suitable for the concentration measurement of a gas. As the fitting curve for the line shape function of the acetylene gas has been deduced from the experiment, the corresponding peak values of the spectral lines can be immediately calculated out from the curve and used for the measurements of different concentrations of acetylene gases. Therefore, the calculation for the line shape function values is greatly simplified. The obtained data of the line shape function of the acetylene gas can be used for remote sensing of the gas, and the proposed method can also be applied for the measurements of line shape functions of other gases.
周 茉1，杨兵初1，陶少华1,2* . 基于谱线线型函数的气体浓度检测技术 [J]. 光谱学与光谱分析, 2015, 35(04): 881-884.
ZHOU Mo1, YANG Bing-chu1, TAO Shao-hua1, 2* . A Detection Technique for Gas Concentration Based on the Spectral Line Shape Function . SPECTROSCOPY AND SPECTRAL ANALYSIS, 2015, 35(04): 881-884.
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