基于量子级联激光吸收光谱技术的NH_(3)吸附性测量研究(特邀)  

Ammonia Adsorption Measurement Based on QCLAS Technique(Invited)

作　　者：杨朝凤 沈晨颖 卢俊城 王娟[2] 邵杰[2] YANG Chaofeng;SHEN Chenying;LU Juncheng;WANG Juan;SHAO Jie(College of Mathematical Medicine,Zhejiang Normal University,Jinhua 321004,China;Key Laboratory of Optical Information Detection and Display Technology of Zhejiang,Zhejiang Normal University,Jinhua 321004,China)

机构地区：[1]浙江师范大学数理医学院,金华321004 [2]浙江师范大学浙江省光信息检测与显示技术研究重点实验室,金华321004

出　　处：《光子学报》2023年第3期148-156,共9页Acta Photonica Sinica

基　　金：国家自然科学基金(No.61775797);浙江省重点研发项目(No.2022C03066);金华市重点科技攻关项目(No.20213032)。

摘　　要：选择中心波长为8.91μm的量子级联激光器作为光源,结合波长调制光谱技术和小体积长光程的光学多通池,开发了一套氨气浓度检测系统。进行不同压力下氨气的直接吸收测量,结果表明谱线选择正确,以及系统搭建可行。配制不同浓度的氨气进行波长调制测量,得到二次谐波信号峰峰值与浓度之间呈现很好的线性关系,其拟合系数为99.50%。氨气浓度在0~100 ppm范围内,二次谐波的平均误差小于3%,其中在较高浓度10~100 ppm范围内,相对误差小于1%,灵敏度为10.35 ppm/V。配制浓度为6.25 ppm的氨气,并通入多通池检测,对系统进行Allan方差分析,系统在最佳积分时间为195 s时的探测极限为121.58 ppb。同时,从管道材料、温度两个方面出发,探究氨气脱附的效果。A strong adsorption effect appears while ammonia passes through a tube or cell,and its polar molecules can easily stick to the wall surface.This results in low sampling quality,slow systemresponse,and low peak concentration,which largely affects the accuracy of gas-monitoring techniques.This work aims to develop a rapid and sensitive monitor system for ammonia concentration,and presents an evaluation method for ammonia desorption at the same time.The developed system of ammonia concentration monitoring makes use of a Quantum Cascade Laser(QCL)operating at 8.91μm as its light source,along with the technique of Wavelength Modulation Spectroscopy(WMS)and multiple-pass cells of low-volume and long-pathlength.Particularly,we study the spectrum of ammonia absorption at 1122.16 cm-1and implement a direct gas absorption monitor of ammonia under different pressures by fitting multiple direct absorption spectrum lines to its Lorentz curve,which analyzes the effects of gas pressures on the absorption spectrum within the specified spectrum range and lays the application foundation for wavelength modulation technology to obtain the 2f ammonia absorption spectrum curve in the target spectrum band.To suppress the system noise,improve its signal-to-noise ratio and further implement the measurement of ammonia wavelength modulation,the optimal pressure for ammonia gas monitor by wavelength modulation technology is hence set to be 0.8 atm.By monitoring the wavelength modulation of ammonia at different concentrations,it shows a perfect linearity between the amplitude of the obtained second-order harmonic wave and gas concentration,with a linear fitting of 99.50%.In the meanwhile,at the ammonia gas concentration of 0~100 ppm,the average error of the second-order harmonic wave is less than 3%,when the relative error is less than 1%at the gas concentration of 10 ppm~100 ppm,along with a sensitivity of 10.35 ppm/V.To evaluate the system stability,ammonia gas at the concentration of 6.25 ppm is prepared to make measurements when flowing

关 键 词：氨气吸附 直接吸收 气体检测 量子级联激光吸收光谱 波长调制 

分 类 号：O433.54[机械工程—光学工程]