Earlier gas measurements of firn air (atmosphere in open pore channels) at polar sites have revealed the occurrence of gas fractionation phenomena during bubble close-off, in addition to well-known thermal and gravitational gas separation. Nevertheless, because of difficulties posed by measurement, little is known about the distribution of air constituents in already closed pores (bubbles) in firn. Herein, we describe the application of high-sensitivity pure rotational Raman spectroscopy, combined with sample immersion in the fluorocarbon-based inert fluid for removing the optical disturbance by diffused reflection. That application efficiently elicits information about nitrogen and oxygen composition ratios (N2/O2 or O2/N2) for each air bubble in firn. The developed methodology presents important implications for elucidating how gas records are formed and modified in the course of pore close-off in polar firn.

中文翻译：

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纯旋转拉曼光谱应用于极地冰中气泡的 N2/O2 分析

除了众所周知的热气体和重力气体分离之外，在极地位置对冷空气（开孔通道中的大气）的早期气体测量揭示了气泡关闭期间气体分馏现象的发生。然而，由于测量带来的困难，人们对森林中已经闭合的孔隙（气泡）中空气成分的分布知之甚少。在这里，我们描述了高灵敏度纯旋转拉曼光谱的应用，结合样品浸入碳氟基惰性流体中，通过漫反射消除光学干扰。该应用程序有效地引出了有关氮和氧组成比（N2/O2或 O2/N2) 对于 firn 中的每个气泡。所开发的方法对阐明在极地冷杉孔隙封闭过程中如何形成和修改气体记录具有重要意义。