$λ$ = 2.06 $μ$ m附近CO $_2$的光腔衰荡光谱：轨道碳观测站-2（OCO-2）“强带”的精确跃迁强度
Cavity ring-down spectroscopy of CO$_2$ near $λ$ = 2.06 $μ$m: Accurate transition intensities for the Orbiting Carbon Observatory-2 (OCO-2) "strong band"
摘要：
CO的$λ$ = 2.06 $μ$ m吸收带被广泛用于大气二氧化碳的遥感，使其与许多重要的自上而下的碳通量测量相关。在这些测量中采用的检索算法中使用的前向模型需要越来越精确的线强度和线形状的数据，从中可以计算吸收截面。为了克服现有谱线表的精度限制，我们使用稳频腔衰荡光谱测量了$^{12}$ C $^{16}$ O $_2$吸收带中的39个跃迁。测量谱线强度，估计的相对组合标准不确定度为$u_r$ = 0.08%。我们使用两种理论模型1预测测量强度的$J$依赖性：具有Herman-Wallis旋转振动校正的一维光谱模型和逐线从头计算偶极矩表面模型[Zak et al. JQSRT 2016;177：31-42]。对于第二种方法，我们只拟合一个因子来重新调整理论积分带强度，使其与测量强度一致。我们发现，后一种方法产生了同样充分的代表性的拟合$J$依赖的强度数据，并提供了最物理的一般表示的结果。我们推荐的积分带强度值等于7.183 $\times$ 10 $^{-21}$ cm分子$^{-1}$ $\pm$ 6 $\times$ 10 $^{-24}$ cm分子$^{-1}$，该值基于重新标度的从头算模型，对应于拟合的标度因子1.0069 $\pm$ 0.0002。将文献强度值与我们的结果进行比较，发现系统偏差范围为$-$ 1.16%至+0.33%。
英文摘要：
The $λ$ = 2.06 $μ$m absorption band of CO$_2$ is widely used for the remote sensing of atmospheric carbon dioxide, making it relevant to many important top-down measurements of carbon flux. The forward models used in the retrieval algorithms employed in these measurements require increasingly accurate line intensity and line shape data from which absorption cross-sections can be computed. To overcome accuracy limitations of existing line lists, we used frequency-stabilized cavity ring-down spectroscopy to measure 39 transitions in the $^{12}$C$^{16}$O$_2$ absorption band. The line intensities were measured with an estimated relative combined standard uncertainty of $u_r$ = 0.08 %. We predict the $J$-dependence of the measured intensities using two theoretical modesl: a one-dimensional spectroscopic model with Herman-Wallis rotation-vibration corrections, and a line-by-line ab initio dipole moment surface model [Zak et al. JQSRT 2016;177:31-42]. For the second approach, we fit only a single factor to rescale the theoretical integrated band intensity to be consistent with the measured intensities. We find that the latter approach yields an equally adequate representation of the fitted $J$-dependent intensity data and provides the most physically general representation of the results. Our recommended value for the integrated band intensity equal to 7.183$\times$10$^{-21}$ cm molecule$^{-1}$ $\pm$ 6$\times$10$^{-24}$ cm molecule$^{-1}$ is based on the rescaled ab initio model and corresponds to a fitted scale factor of 1.0069 $\pm$ 0.0002. Comparisons of literature intensity values to our results reveal systematic deviations ranging from $-$1.16 % to +0.33 %.
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