The spectrum of dicarbon (C2) is important in astrophysics and for spectroscopic studies of plasmas and flames. The C2 spectrum is characterized by many band systems with new ones still being actively identified; astronomical observations involve eight of these bands. Recently, Furtenbacher et al. (2016, Astrophys. J. Suppl., 224, 44) presented a set of 5699 empirical energy levels for 12C2, distributed among 11 electronic states and 98 vibronic bands, derived from 42 experimental studies and obtained using the MARVEL (Measured Active Rotational-Vibrational Energy Levels) procedure. Here, we add data from 13 new sources and update data from 5 sources. Many of these data sources characterize high-lying electronic states, including the newly detected 3Pig state. Older studies have been included following improvements in the MARVEL procedure which allow their uncertainties to be estimated. These older works in particular determine levels in the C1Pig state, the upper state of the insufficiently characterized Deslandres-d'Azambuja (C1Pig-A1Piu) band. The new compilation considers a total of 31323 transitions and derives 7047 empirical(MARVEL) energy levels spanning 20 electronic and 142 vibronic states. These new empirical energy levels are used here to update the 8states C2 ExoMol line list. This updated line list is highly suitable for high-resolution cross-correlation studies in astronomical spectroscopy of, for example, exoplanets, as 99.4% of the transitions with intensities over 10^(-18) cm/molecule at 1000 K have frequencies determined by empirical energy levels.

中文翻译：

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12C2 的 MARVEL 数据集和 ExoMol 线列表的更新

二碳 (C2) 的光谱在天体物理学和等离子体和火焰的光谱研究中很重要。C2 频谱的特点是有许多频段系统，新的频段系统仍在积极识别中；天文观测涉及其中八个波段。最近，Furtenbacher 等人。(2016, Astrophys. J. Suppl., 224, 44) 提出了 12C2 的 5699 个经验能级，分布在 11 个电子态和 98 个振动带中，来自 42 项实验研究并使用 MARVEL（测量的主动旋转-振动能级）程序。在这里，我们添加来自 13 个新来源的数据并更新来自 5 个来源的数据。许多这些数据源表征高位电子状态，包括新检测到的 3Pig 状态。在 MARVEL 程序的改进之后，旧的研究已被包括在内，从而可以估计其不确定性。这些较旧的作品特别确定了 C1Pig 状态的水平，这是未充分表征的 Deslandres-d'Azambuja (C1Pig-A1Piu) 波段的上层状态。新汇编总共考虑了 31323 个跃迁，并推导出了 7047 个经验 (MARVEL) 能级，跨越 20 个电子态和 142 个振动态。这些新的经验能级在这里用于更新 8states C2 ExoMol 线列表。这个更新的线列表非常适用于天文光谱中的高分辨率互相关研究，例如系外行星，因为在 1000 K 强度超过 10^(-18) cm/分子的跃迁中有 99.4% 的频率由下式确定经验能级。