Abstract：An accurate line-by-line integral trace gas absorption model is presented in the present article. It is for mid-infrared band and can be used in the study on and application to detecting trace gas (or pollution gas). First of all, two algorithms of trace gas radioactive properties, line-by-line integral method and band model method, were introduced. The merits and demerits of each were compared. Several recent developed line-by-line integral calculation models were also introduced. Secondly, the basic principle of line-by-line integral trace gas absorption calculation model was described in detail. The absorption coefficient is a function of temperature, frequency (wave number), pressure, gas volume mixing ratio and constants associated with all contributing line transitions. The average monochromatic absorption coefficient at a given frequency of a given gas species can be written as the product of the number density of the molecular species to which the spectral line belongs, the line intensity and a line shape factor. Efficient calculation of the line shape factor may be required for different atmospheric conditions. In the lower atmosphere, the shape of spectral lines is dominated by pressure broadening and can be represented most simply by the Lorentz line shape factor. At high altitudes, the shape of spectral lines is governed by Doppler broadening At intermediate altitudes, they can be modeled using the Voigt line shape factor, a convolution of the Lorentz and Doppler line shape factors. Finally, in the section of experiment, the results calculated by model were compared with that measured by Fourier transform infrared spectrometer. As an instance, the model was applied to the detectors design of NDIR (non-dispersive infrared ) technology and the relationship between signal intensity of detectors and concentration of CO2/CO was simulated by model. Available concentration range of detector was given by calculating the results of the model. It is based on HITRAN molecular spectroscopic database. Far wings, temperature correction and instruments function were all calculated for the absorption coefficient calculation. Infrared absorption characters of various gases in atmosphere can be simulated by the model.
方静,刘文清,张天舒. 逐线积分气体吸收模型及其在NDIR气体检测中的应用[J]. 光谱学与光谱分析, 2008, 28(06): 1269-1272.
FANG Jing,LIU Wen-qing,ZHANG Tian-shu. A Line-by-Line Trace Gas Absorption Model and Its Application in NDIR Gas Detection Technology. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2008, 28(06): 1269-1272.
[1] Goody R M, Yung Y L. Atmospheric Radiation: Theoretical Basis. Oxford: Oxford University Press, 1989. 125. [2] Rothman L S, Jacquemart D, Barbe A, et al. Journal of Quantitative Spectroscopy & Radiative Transfer，2005，96(2)：139. [3] Smith H J P, Dube D J, Gardner M E. FASCODE-Fast Atmospheric Signature Code(Spectral Transmittance Radiance). AFGL-TR-78-0081, Scinetific Report, No.2, 1978. [4] Clough S A, Kneizys F X, Anderson G P. The Updated LBLRTM_Ver5.21. http://www.rtweb.aer.com/, 2000. [5] ZHANG Hua, SHI Guang-yu(张 华，石广玉). Chinese Journal of Atmospheric Sciences(大气科学), 2000, 24(1): 111. [6] ZHOU Xiu-ji, TAO Shan-chang, YAO Ke-ya(周秀骥，陶善昌，姚克亚). High Atmospheric Physics(高等大气物理学). Beijing：Atmosphere Press (北京: 气象出版社), 1991. 690. [7] GAO Min-guang, LIU Wen-qing, ZHANG Tian-shu, et al(高闽光, 刘文清, 张天舒，等). Spectroscopy and Spectral Analysis（光谱学与光谱分析）, 2006, 26(1): 47. [8] Crookell A, Kansakoski M. Proc. SPIE-Int. Soc. Opt. Eng.(USA), 2001, 4205: 35.
