痕量气体的高灵敏红外光谱检测技术

发布时间：2018-01-07 02:07

本文关键词：痕量气体的高灵敏红外光谱检测技术　出处：《中国科学院光电技术研究所》2017年博士论文　论文类型：学位论文

【摘要】：光腔衰荡光谱(CRDS)是一种灵敏度显著高于传统吸收光谱的检测技术,被广泛应用于气体吸收光谱的测量。吸收光谱由分子的内部结构决定,每一种气体都有其独特的吸收光谱,通过对分子光谱的研究可了解原子内部的结构,或对样品所含成分进行定性和定量分析。大部分气体在红外波段都有丰富的吸收谱线。本文分别以脉冲和连续量子级联激光器为光源,在中红外波段,开展了基于光腔衰荡光谱技术的高灵敏痕量气体检测技术的研究。本文介绍了传统光谱检测技术以及光腔衰荡技术,推导了几种常见的分子光谱线型函数,搭建了以脉冲量子级联激光器为光源的光腔衰荡光谱技术痕量气体检测平台。对实验室空气和高纯氮气中的甲烷吸收谱线进行了测量。利用HITRAN数据库中的吸收谱线对激光器波长做了绝对波长的校准。利用光腔衰荡光谱技术结合水汽的吸收谱线测量了量子级联激光器的光谱线宽。分析了激光器谱线线宽对小分子气体吸收谱线测量的影响,并通过修正曲线修正了甲烷和水汽吸收谱线。针对传统吸收光谱技术聚焦于小分子气体检测的问题。本文探索了利用宽调谐的激光光源结合脉冲光腔衰荡光谱技术,获得内容更丰富的气体吸收谱,开展了具有宽谱吸收的大分子挥发性有机气体浓度检测的研究。并利用实验装置测量了实验室常用挥发气体(酒精,乙醚,丙酮),与PNNL数据库进行了比较,编写多组分分析算法实现了多种不同浓度挥发气体的同时测量,对乙醇、乙醚和丙酮的检测限分别为157 ppb、60 ppb和280 ppb。以5.2um可调谐量子级联激光器为光源,搭建了基于连续光腔衰荡光谱技术的痕量气体检测系统,对系统做阿伦(Allan)方差分析,优化了信号平均次数。在水汽吸收谱线更为丰富的中红外区域,实现了高纯氮气中痕量水汽的检测,对水汽的检测限达到24.8ppb。通过理论分析NO及口腔气体中干扰气体组分红外光谱分布特征,确定1900cm-1为NO最佳测量波长。搭建基于连续光腔衰荡光谱技术实验装置,测量了高纯氮气中痕量浓度的NO,检测限为0.45ppb。在此基础上,对测试压强做优化,并实现了实际口腔气中痕量浓度NO的检测,检测限为0.41ppb,同时开展了人体呼出口腔气体中NO成分的准实时测量和监测。本文还提出了一种基于光腔衰荡光谱技术测量气体池气密性的方法,利用水汽的吸收光谱,实现了系统漏率的检测;提出了一种基于光腔衰荡光谱技术和气体吸收谱线压力展宽效应的压力计校准方法。通过高分辨的测量窄线宽气体吸收光谱得到压强信息,实现压强检测和高精度小量程的压力计校准。系统对压强的检测限优于0.18KPa。利用测试谱线线宽与压强的关系得到水汽的压力展宽系数与HITARN数据库参考值一致。
[Abstract]:CRDS is a technique with higher sensitivity than the traditional absorption spectrum, which is widely used in the measurement of gas absorption spectrum. The absorption spectrum is determined by the internal structure of the molecule. Each gas has its unique absorption spectrum, and the structure of the atom can be understood by studying the molecular spectrum. Or qualitative and quantitative analysis of the composition of the sample. Most of the gases in the infrared band have rich absorption lines. In this paper, pulse and continuous quantum cascade lasers as the light source, in the mid-infrared band. The research of high sensitive trace gas detection technology based on optical cavity ring-down spectroscopy is carried out. In this paper, the traditional spectral detection technology and the optical cavity ring-down technique are introduced, and several common molecular spectral lineal functions are derived. A platform for detecting trace gases by cavity ring-down spectroscopy using pulsed quantum cascade lasers as light source has been set up. The absorption spectra of methane in laboratory air and high purity nitrogen have been measured. The HITRAN database has been used to measure the absorption spectra of methane. The spectral linewidth of a quantum cascade laser is measured by cavity ring-down spectroscopy combined with the absorption line of water vapor. The spectrum linewidth of a quantum cascade laser is analyzed. The influence of subgas absorption line measurement. The absorption lines of methane and water vapor were corrected by modifying the curve. Aiming at the problem of traditional absorption spectrum focusing on the detection of small molecular gases, the wide tuning laser source combined with pulse cavity ring-down spectroscopy was explored in this paper. Art. More abundant gas absorption spectra were obtained, and the determination of volatile organic gas concentration of macromolecules with wide spectrum absorption was carried out, and the commonly used volatile gases (alcohol, ether) were measured by experimental apparatus. Compared with PNNL database, acetone can be used to measure volatile gases with different concentrations. The detection limits of ethanol, ether and acetone are 157 ppb. Using 5.2um tunable quantum cascade laser as the light source, a trace gas detection system based on continuous cavity ring-down spectroscopy has been set up with 60 ppb and 280 ppb. The analysis of variance of Allan in the system optimizes the average number of signals and realizes the detection of trace water vapor in high purity nitrogen in the mid-infrared region where the absorption lines of water vapor are more abundant. The detection limit of water vapor is 24.8 ppb. the spectral distribution characteristics of no and the component of interference gas in oral gas are analyzed theoretically. The optimum measurement wavelength of no was determined at 1900 cm ~ (-1). Based on the continuous cavity ring-down spectroscopy, the trace concentration of no in high purity nitrogen was measured. The detection limit is 0.45 ppb. on this basis, the test pressure is optimized, and the detection limit of trace concentration of no in oral gas is 0.41 ppb. At the same time, the quasi-real-time measurement and monitoring of no in human exhaled oral gas were carried out. A method based on optical cavity ring-down spectroscopy was proposed to measure the air tightness of gas pool, and the absorption spectrum of water vapor was used. The leakage rate of the system is detected; A pressure gauge calibration method based on cavity ring-down spectroscopy and pressure broadening effect of gas absorption spectrum is proposed. The pressure information is obtained by high resolution measurement of narrow linewidth gas absorption spectrum. The pressure detection limit of the system is better than 0.18 KPA. The pressure broadening coefficient of water vapor and HITAR can be obtained by using the relationship between line width and pressure. The reference value of N database is consistent.
【学位授予单位】：中国科学院光电技术研究所
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN248;O433

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