The CIPM list "Recommended values of standard frequencies": 2021 update
arxiv(2024)
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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