Limitations of Spectral Subtraction in the Elimination of Infrared Water Vapor Bands
YU Min-xing1, WANG Hai-shui1*, ZHANG Yun-hong2*
1. School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, China
2. Institute of Chemical Physics, School of Chemistry, Beijing Institute of Technology, Beijing 100081, China
Abstract：Spectral subtraction is a powerful and conventional tool for the elimination of background interferences, but this technique has been suffered from severe limitations in the case of atmospheric water vapor. In order to understand the real reasons of the problems above , IR spectra of water vapor at different humidity have been investigated. The following conclusions have been reached: (1) The spectral features of water vapor will change as the relative humidity of air changes. Namely, if the spectrum of atmospheric air with x% relative humidity is given, we cannot predict and obtain the spectrum of air with y% humidity regardless of how carefully the scaling factor has been chosen. In general, spectral subtraction is not a good practice to remove water vapor interferences. (2) The relative composition of water clusters (H2O)n changes with the relative humidity, and this is the main reason of spectral subtraction limitation. (3) The spectrum of water vapor between relative humidity x% and y% can be matched near perfectly by a combination of x% spectrum and y% spectrum. This provides a new and effective way for the elimination of water vapor interferences. (4) The high efficiency of the humidity titration method has been demonstrated experimentally.
余敏行，王海水，张韫宏. 红外光谱差减技术扣除水汽吸收干扰的局限性[J]. 光谱学与光谱分析, 2017, 37(06): 1673-1677.
YU Min-xing, WANG Hai-shui, ZHANG Yun-hong. Limitations of Spectral Subtraction in the Elimination of Infrared Water Vapor Bands. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2017, 37(06): 1673-1677.
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