快速、精确地测量微量气体浓度的技术在大气质量分析、环境污染检测等领域具有广泛的用途.在红外光谱检测技术中,气体吸收光谱的谱线线型函数是定量测量气体浓度的一个重要参量,而如何准确和快速地得到气体谱线线型函数值是气体浓度测量中的一个关键问题.首先从理论上分析了谱线线型函数,得出计算谱线线型函数的一般方法及探讨了气体浓度与谱线线型函数峰值之间的关系.然后,利用可调激光器及光谱仪检测系统测量了乙炔在1 515～1 545 nm波长范围内的吸收光谱,再通过Lambert-Beer定律计算得到在不同频率下的谱线线型函数峰值,最后利用程序拟合出该波段内气体的谱线线型函数峰值分布曲线,并与Voigt线型函数理论计算值进行了比较,发现理论计算的谱线线型函数峰值仍存在一定的偏差.相比理论计算结果,所提出的检测方法得到的乙炔浓度与真实的乙炔浓度值更加吻合,表明了通过实验确定的谱线线型函数的经验公式可以更好地用于气体浓度的检测.由于利用实验测量值获得了谱线线型函数峰值分布的拟合曲线,因此可以快速准确地计算出所对应的谱线线型函数峰值,从而大大地简化了线型函数的计算过程.实验所获得的数据可应用于光学遥测乙炔气体浓度,且提供的方法也可以应用到其他气体的谱线线型函数峰值的测量中.

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.