基于红外检测的甲烷传感器中光谱吸收理论的研究

摘要

Molecular spectroscopy absorption spectrum theory is the theoretical basis of the optical fiber gas sensor, which has important significance for the detection of toxic gas concentration with fiber infrared method. According to the Beer-Lambert theory, this paper researches from the quantitative analysis of concentration of gaseous methane(CH4) and molecular parameters theory study, and then through the analysis of the absorption of CH4 gas line to conclude general method of the absorption coefficient detection. When the pressure is lower than 0.02atm, dominant Doppler broadened, Gaussian alignment fitting is used to get α(ν). When the pressure is higher than 0.1atm collision broadening is dominant, Lorentzian alignment fitting is used, and when the pressure is between 0.02-0.1 atm, ttwo are widened, Voigt is better. In theory it is a very good result.%分子光谱理论是光谱吸收式光纤气体传感器的理论基础，对于光纤红外法检测有毒气体的浓度具有重要意义。根据朗伯-比尔（Beer-Lambert）理论，首先从甲烷（CH4）气体浓度的定量分析以及分子参数的理论进行研究，再通过分析 CH4气体的吸收线得出其吸收系数α(v)的一般方法。由分析得当气体压强P＜0.02 atm时多普勒展宽占优势，用高斯线型拟合吸收线；当P＞0.l atm时碰撞展宽占优势，用洛仑兹线型拟合吸收线；当0.02 atm＜P＜0.l atm时两种展宽都存在，这时用伏格特线型拟合吸收线，理论上得到很好的结果。