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Development of Liquified Air/Fourier Transform Infrared Spectroscopic Method for Simultaneous Measurement of Atmospheric Trace Gases

大气痕量气体同步测量的液化空气/傅里叶变换红外光谱法的发展

基本信息

批准号：
07558193
负责人：
AKIMOTO Hajime
金额：
$ 1.79万
依托单位：
Research Center for Advanced Science and Technology, University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

A novel method for simultaneous measurement of atmospheric trace gases using liquified air/Fourier transform infrared spectroscopy has been developed. The equipment consists of Fourier transform infrared spectrometer, transfer optics and a cryostat containing optical light pipe. The cryostat consists of helium refrigerator, and a light pipe (4 mm i. d. and 20 cm long, gold coated). The air introduced into the cryostat was liquified by the helium refrigerator and the liquified air was introduced into the light pipe. Infrared spectrum of the liguified air was taken by the FTIR spectrometer with a resolution of 1 cm^<-1>.Carbon monoxide (1.6 ppm in synthesized air) gave an absorption band at 2140 cm^<-1> with a band-width of 20 cm^<-1>. Methane (10 ppm in synthesized air) gave absorption band at 1305 and 3016 cm^<-1> with band-width of 10 and 20 cm^<-1>, respectively. Those bands were well separated from large saturated peaks of CO_2 and H_2O contained in air and found to be used for quantitative measurement of CO and CH_4. Detection limit estimated from S/N ratio of 3 was 35 ppb for CO,and 23 and 40 ppb for CH_4 using the bands of 1305 and 3016 cm-1, respectively. These detection limit is low enough compared with the typical atmospheric concentration of CO (100-500 ppb) and CH_4 (1.7-2.0 ppm). The proposed method was found to be applicable for the detection of these trace gases in the atmosphere.

提出了一种利用液化空气/傅里叶变换红外光谱同时测量大气痕量气体的新方法。该装置由傅里叶变换红外光谱仪、传输光学系统和含光学导光管的低温恒温器组成。该低温恒温器由氦制冷机、光管（4 mm i. D. 20厘米长，镀金）。引入低温恒温器的空气被氦制冷机液化，液化的空气被引入光管。通过FTIR光谱仪以1 cm-1的分辨率获取液化空气的红外光谱<-1>。一氧化碳（在合成空气中为1.6 ppm）在2140 cm-1处产生吸收带<-1>，带宽为20 cm-1<-1>。甲烷（在合成空气中10 ppm）分别在1305和3016 cm-2处产生<-1>带宽为10和20 cm-2<-1>的吸收带。这些谱带与空气中CO_2和H_2O的大饱和峰分离良好，可用于CO和CH_4的定量测定。在1305和3016 cm-1波段，根据信噪比为3估算的检测限，CO为35 ppb，CH_4为23和40 ppb。与典型的大气中CO（100-500 ppb）和CH_4（1.7- 2.0ppm）浓度相比，本方法的检出限足够低。所提出的方法被认为是适用于检测这些痕量气体在大气中。