Open-path measurements of atmospheric gas species in the air, including volatile organic compounds, are essential to quantify emissions from sources like oil and gas, forest fires, and industry. Here, we extend open-path dual-comb spectroscopy to probe the fundamental mid-infrared C-H stretch modes of volatile organic compounds over up to 1 km long open-air paths. The spectrometer’s high resolution and accuracy facilitates suppression of strong spectral clutter from atmospheric water and methane, allowing quantitative measurements of released acetone and isopropanol with a $1-\sigma$ sensitivity of $5.7\mathrm{ppm}·\mathrm{m}$ and $2.4\mathrm{ppm}·\mathrm{m}$, respectively, and of ambient atmospheric ethane with a $1-\sigma$ sensitivity of 0.4 ppb, measured with 1 min time resolution over hours. These results underline the potential of dual-comb spectroscopy for quantifying emissions.

中文翻译：

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跨越长距离开放路径的挥发性有机化合物的中红外双梳光谱

对空气中的大气气体种类（包括挥发性有机化合物）进行开路测量对于量化石油和天然气，森林大火以及工业等排放源的排放至关重要。在这里，我们扩展了开放路径双梳状光谱技术，以探测长达1 km的露天路径上的挥发性有机化合物的基本中红外CH拉伸模式。该光谱仪的高分辨率和准确性有助于抑制大气中的水和甲烷产生的强光谱杂波，从而可以定量分析释放的丙酮和异丙醇。$\mathrm{1个}-\sigma$ 的敏感性 $5.7\mathrm{百万分之几}·\mathrm{米}$ 和 $2.4\mathrm{百万分之几}·\mathrm{米}$以及环境空气中的乙烷 $\mathrm{1个}-\sigma$灵敏度为0.4 ppb，以1分钟的时间分辨率测量。这些结果强调了双梳子光谱法在定量排放方面的潜力。