Molecular diagnostics are a primary tool of modern chemistry, enabling researchers to map chemical reaction pathways and rates to better design and control chemical systems. Many chemical reactions are complex, involving multiple species and reaction pathways occurring on µs or shorter timescales. Existing diagnostic approaches provide a subset of chemical and thermodynamic information. Here we optimize across many diagnostic objectives by introducing a high-speed and broadband, mid-infrared dual-frequency-comb absorption spectrometer. The optical bandwidth of >1000cm−1 covers absorption fingerprints of many species with spectral resolution <0.03cm−1 to accurately discern their absolute quantities. Key to this advance are 1 GHz pulse repetition rate mode-locked frequency combs covering the 3–5 µm region that enable a spectral acquisition rate of 290cm−1 per 17.5 µs per detector for in situ tracking of fast chemical process dynamics. We demonstrate this system to quantify the abundances and temperatures of each species in the complete reactants-to-products breakdown of 1,3,5-trioxane, which exhibits a formaldehyde decomposition pathway that is critical to modern low-temperature combustion systems. By maximizing the number of observed species and improving the accuracy of temperature and concentration measurements, this spectrometer provides a pathway for modern chemistry approaches such as combining chemical models with machine learning to constrain or predict complex reaction mechanisms and rates.

中文翻译：

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快速化学反应的 GHz 重复率中红外频率梳状光谱


分子诊断是现代化学的主要工具，使研究人员能够绘制化学反应路径和速率，以更好地设计和控制化学系统。许多化学反应都很复杂，涉及多种物质和在微秒或更短的时间尺度上发生的反应途径。现有的诊断方法提供化学和热力学信息的子集。在这里，我们通过引入高速宽带中红外双频梳吸收光谱仪来优化许多诊断目标。光带宽>1000cm −1涵盖许多物种的吸收指纹，光谱分辨率 <0 id=30>−1准确地辨别它们的绝对数量。这一进步的关键是覆盖 3–5 µm 区域的 1 GHz 脉冲重复率锁模频率梳，可实现 290cm 的光谱采集率−1每个探测器每 17.5 µs就地跟踪快速化学过程动态。我们证明该系统可以量化 1,3,5-三恶烷从反应物到产物的完整分解过程中每种物质的丰度和温度，该分解过程表现出对现代低温燃烧系统至关重要的甲醛分解途径。通过最大限度地增加观察到的物种数量并提高温度和浓度测量的准确性，该光谱仪为现代化学方法提供了一条途径，例如将化学模型与机器学习相结合，以约束或预测复杂的反应机制和速率。