A cavity ring-down spectroscopy apparatus employing a pulsed quantum cascade laser operating near 1027 cm-1 (9.7 μm) is investigated for trace ammonia detection. The trace ammonia in human breath and clean room atmosphere are measured and analyzed. A sensitivity of 10 ppb has been demonstrated for ammonia detection. The effects of the spectral line-width on the measurement accuracy and sensitivity of the system are analyzed. The measurement accuracy and sensitivity of the apparatus decrease with the increasing laser spectral line-width. The measurement results can be corrected by taking into account of the line-width effect in data analysis.%采用基于红外脉冲量子级联激光器的高灵敏光腔衰荡光谱(Cavity ring-down spectroscopy)技术建立了氨气在1027 cm-1(9.7 μm)附近的吸收光谱痕量检测实验装置.使用该装置对人体口腔呼出气体以及超净实验室环境中氨气成份进行了测量和分析,氨气的检测灵敏度达到10 ppb.模拟分析了激光器光谱线宽对测量结果和系统检测灵敏度的影响,随着激光器光谱线宽的增加,测量结果偏低,系统检测灵敏度下降.为了减小光源线宽对测量结果的影响,通过修正曲线对测量数据进行修正,得到了较好的结果.
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