RATIONALE Unravelling the biogeochemical cycle of the potent greenhouse gas nitrous oxide (N2 O) is an underdetermined problem in environmental sciences due to the multiple involved source and sink processes, which complicates mitigation of its emissions. Measuring the doubly isotopically substituted molecules (isotopocules) of nitrous oxide can add new opportunities to fingerprint and constrain its cycle. METHODS We present a laser spectroscopic technique to selectively and simultaneously measure the eight most abundant isotopocules of N2 O, including three doubly substituted species - so called "clumped isotopes". For the absolute quantification of individual isotopocule abundances, we propose a new calibration scheme that combines thermal equilibration of a working standard gas with a direct mole fraction-based approach. RESULTS This method is validated for a large range of isotopic composition values by comparison with other established methods (laser spectroscopy using conventional isotopic scale and isotope-ratio mass spectrometry). Direct intercomparison with recently developed ultra-high-resolution mass spectrometry shows clearly the advantages of the new laser technique, especially with respect to site specificity of isotopic substitution in the N2 O molecule. CONCLUSIONS Our study represents a new methodological basis for the measurements of both singly substituted and clumped N2 O isotopes. It bears a high potential to stimulate future research in the N2 O community by establishing a new class of reservoir-insensitive tracers and molecular-scale insights.

中文翻译：

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通过中红外激光光谱对N2 O中成簇同位素的初步研究和绝对校准。

理由：由于源和汇过程涉及多个过程，因此难以有效解决温室效应一氧化二氮（N2 O）的生物地球化学循环问题，这在缓解环境污染方面十分复杂。测量一氧化二氮的同位素同位素双取代分子（同位素）可以增加指纹识别的新机会并限制其循环。方法我们介绍了一种激光光谱技术，可选择性地同时测量N2 O的八个最丰富的同位素，包括三个双取代物种-所谓的“聚集同位素”。对于单个同位素的丰度的绝对定量，我们提出了一种新的校准方案，该方案将工作标准气体的热平衡与基于直接摩尔分数的方法相结合。结果与其他已建立的方法（使用常规同位素规模的激光光谱法和同位素比质谱法）相比，该方法可用于各种同位素组成值。与最近开发的超高分辨率质谱的直接比较清楚地表明了新激光技术的优势，特别是在N2 O分子中同位素取代的位点特异性方面。结论我们的研究代表了一种新的方法学基础，可用于测量单取代和成簇的N2 O同位素。通过建立一类新型的对储层不敏感的示踪剂和分子尺度的见识，它具有激发N2 O界未来研究的巨大潜力。