Daghestani Nart S, Brownsword Richard, Weidmann Damien
Opt Express. 2014 Dec 15;22 Suppl 7:A1731-43. doi: 10.1364/OE.22.0A1731.
Atmospheric methane concentration levels were detected using a custom built laser dispersion spectrometer in a long open-path beam configuration. The instrument is driven by a chirped distributed feedback mid-infrared quantum cascade laser centered at ~1283.46 cm and covers intense rotational-vibrational transitions from the fundamental ν band of methane. A full forward model simulating molecular absorption and dispersion profiles, as well as instrumental noise, is demonstrated. The instrument's analytical model is validated and used for quantitative instrumental optimization. The temporal evolution of atmospheric methane mixing ratios is retrieved using a fitting algorithm based on the model. Full error propagation analysis on precision gives a normalized sensitivity of ~3 ppm.m.Hz for atmospheric methane.
使用定制的长开放路径光束配置的激光色散光谱仪检测大气甲烷浓度水平。该仪器由中心波长约为1283.46厘米的啁啾分布反馈中红外量子级联激光器驱动，覆盖甲烷基频ν带的强烈转动-振动跃迁。展示了一个模拟分子吸收和色散分布以及仪器噪声的完整正向模型。对该仪器的分析模型进行了验证，并用于定量仪器优化。使用基于该模型的拟合算法反演大气甲烷混合比的时间演变。对精度进行的全误差传播分析得出大气甲烷的归一化灵敏度约为3 ppm·m·Hz。
