CIPM“标准频率推荐值”清单：2021年更新
The CIPM list "Recommended values of standard frequencies": 2021 update
AI总结：
本文介绍CIPM标准频率推荐值2021年更新，通过独立算法和相关性分析处理全球钟比对数据，给出一致的绝对频率与频率比值，并降低光学SRS不确定度。
摘要：
本文详细说明了支撑国际计量委员会（CIPM）推荐的标准参考频率值清单2021年更新的分析工作。此次更新聚焦于作为秒的次级表示（SRS）或被视为潜在SRS的一部分原子跃迁。与2015年和2017年的此前更新一样，研究采用分析超定数据集的方法，以最佳利用全球已发表的钟比对数据体系。为确保这些方法稳健，研究使用两种不同算法进行了三次独立计算。2021年更新与此前更新的不同之处在于，详细考虑了输入数据之间的相关性；这一步骤被证明对于获得无偏频率值并避免低估其不确定度十分重要。其不同之处还体现在评估输入数据以及为推荐频率值赋予不确定度的程序上：研究调整了以往做法，以生成一个完全一致的输出数据集，其中既包括频率比值，也包括绝对频率。在预期将依据一个或多个光频跃迁重新定义秒的背景下，这些变化具有重要意义，因为在重新定义之前，光频比值测量对于验证光钟的国际一致性至关重要。同时，由本分析带来的光学SRS不确定度降低，显著提高了基于这些跃迁的次级频率标准在驾驭国际原子时（TAI）中所能具有的权重。
英文摘要：
This paper gives a detailed account of the analysis underpinning the 2021 update to the list of standard reference frequency values recommended by the International Committee for Weights and Measures (CIPM). This update focused on a subset of atomic transitions that are secondary representations of the second (SRS) or considered as potential SRS. As in previous updates in 2015 and 2017, methods for analysing over-determined data sets were applied to make optimum use of the worldwide body of published clock comparison data. To ensure that these methods were robust, three independent calculations were performed using two different algorithms. The 2021 update differed from previous updates in taking detailed account of correlations among the input data, a step shown to be important in deriving unbiased frequency values and avoiding underestimation of their uncertainties. It also differed in the procedures used to assess input data and to assign uncertainties to the recommended frequency values, with previous practice being adapted to produce a fully consistent output data set consisting of frequency ratio values as well as absolute frequencies. These changes are significant in the context of an anticipated redefinition of the second in terms of an optical transition or transitions, since optical frequency ratio measurements will be critical for verifying the international consistency of optical clocks prior to the redefinition. In the meantime, the reduced uncertainties for optical SRS resulting from this analysis significantly increases the weight that secondary frequency standards based on these transitions can have in the steering of International Atomic Time (TAI).
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