关键词: 氨气/
可调谐半导体激光吸收光谱技术/
线强/
不确定度
English Abstract
Measurements of line strengths for some lines of ammonia in 6611-6618 cm-1
Nie Wei1,2,Kan Rui-Feng1,
Xu Zhen-Yu1,
Yang Chen-Guang1,
Chen Bing1,
Xia Hui-Hui1,2,
Wei Min1,2,
Chen Xiang1,2,
Yao Lu1,
Li Hang1,2,
Fan Xue-Li1,
Hu Jia-Yi1
1.Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China;
2.University of Science and Technology of China, Hefei 230026, China
Fund Project:Project supported by the National Key Scientific Instrument and Equipment Development Project of China (Grant No. 2014YQ060537).Received Date:21 August 2016
Accepted Date:30 November 2016
Published Online:05 March 2017
Abstract:The target gas molecular absorption spectrum parameters especially line strengths are very important for measuring temperature and concentration with tunable diode laser absorption spectroscopy (TDLAS) technique. Usually, researchers use line strengths which come from spectrum database, like HITRAN and GEISA and HITEMP spectra database, but those database include values from the theoretical computation, as is well known, there is a big error between the theoretical value and the actual value. In order to modify the line strengths of the database, 20 ammonia spectrum absorption lines in a wavenumber range between 6611 and 6618 cm-1 are measured at different pressures by using direct tunable diode laser absorption spectroscopy (dTDLAS) technique. The measurement procedure is repeated at least 10 times at each pressure, and then average value is calculated. Voigt fitting is used to obtain all line integral area, and then the line integral area is obtained by linear fitting. The slope of the fitting straight line equals line strength. Uncertainty analysis is given for the measurements. The measured linestrength is a function of integrated area, temperature, pressure, species mole fraction and effective path length. So, the calculated linestrength uncertainties based on those parameters uncertainties, and the uncertainties of pressure, species mole fraction and effective path length are similar for all transitions with P =0.25%, =0.2%, and L =0.4%. The uncertainties of the integrated area and temperature are related to different lines, and their values come from the actual measurement. In the end, uncertainty propagation formula is used to calculate linestrength uncetainty. Uncertainties of our measured line strengths are in a 0.81%-3.33% range. Our measured line strength values are different from line strengths in the HITRAN 2012 database, and the deviations are in 0.51%-17.28% range.
Keywords: ammonia/
tunable diode laser absorption spectroscopy/
line strengths/
uncertainties
