A Line-by-line Trace Gas Absorption Model and Its Application in FTIR Gas Detection
逐线积分气体吸收模型及其在FTIR气体检测中的应用

An accurate line-by-line trace gas absorption model which is useful for the theoretical research and engineering application of atmosphere trace gas(or pollution gas)detection in the mid- infrared waveband is presented.Because the HITRAN molecular spectrum database is used and the factors such as spectral line width,far wings,temperature correction and spectral resolution are taken into account,the model can be used to simulate the infrared absorption characters of various gases in atmosphere effectively.The algorithm of the model is described in detail and the results calculated by the model are compared with those measured by the Fourier Transform Infrared Spectrometer(FTIR).The practical application of the absorption model in the FTIR gas detection technoloy is given.The model is used to analyze the measured FTIR spectrum quantitatively and simulate the reference spectrum which is fitted to the measured spectra by using a nonlinear least square algorithm.Thus,the retrieval of the concentration of several kinds of gases can be implemented without reference gases at the same time.