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首页> 外文会议>RIAO/OPTILAS 2004 >Photothermal beam deflection applied to SO_2 trace detection
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Photothermal beam deflection applied to SO_2 trace detection

机译：光热束偏转应用于SO_2痕量检测

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摘要

We present the application to environmental monitoring of a compact setup for in situ trace gas detection based on photothermal beam deflection (mirage effect) spectroscopy. Gas traces measurements are performed by detecting the time-varying component of the photothermal deflection of a red diode laser beam, propagating inside the region where a pollutant is excited by another laser. In this work, detection of traces of SO_2 in an mixture with Nitrogen at atmospheric pressure enclosed in a glass cell, was performed using the fourth-harmonic pulses of a 10 Hz Nd:YAG laser. It was verified by FTIR spectroscopy that negligible SO_2 destruction was produced after irradiation of high pressure mixtures with 10~5 UV pulses. Several beam sizes and propagating angles for the UV and visible laser were tested and evaluated in order to overcome parasitic signals due to unwanted absorption in optical elements. With this setup we reached a detection limit of 5 ppbV in a hundred-second averaging time span but we estimate sub-ppbV levels can be reached by simple changes in the geometry for improving the signal to noise ratio.
机译：我们介绍了一种基于光热束偏转（镜像效应）光谱的现场痕量气体检测的紧凑型装置在环境监测中的应用。通过检测红色二极管激光束的光热偏转随时间变化的分量（在污染物被另一激光激发的区域内传播）来执行气体痕量测量。在这项工作中，使用10 Hz Nd：YAG激光的四次谐波脉冲，在封闭于玻璃池中的大气压下与氮气的混合物中痕量的SO_2进行了检测。 FTIR光谱证明，用10〜5个UV脉冲辐照高压混合物后，产生的SO_2破坏可忽略不计。测试和评估了紫外和可见激光的几种光束尺寸和传播角度，以克服由于光学元件中有害吸收而引起的寄生信号。通过这种设置，我们在100秒的平均时间跨度内达到了5 ppbV的检测极限，但我们估计，通过简单改变几何形状以改善信噪比，可以达到亚ppbV级别。

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